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Diffstat (limited to 'railties/guides/source')
| -rw-r--r-- | railties/guides/source/active_record_basics.textile | 57 | ||||
| -rw-r--r-- | railties/guides/source/active_record_querying.textile | 2 | ||||
| -rw-r--r-- | railties/guides/source/active_record_validations_callbacks.textile | 121 | ||||
| -rw-r--r-- | railties/guides/source/asset_pipeline.textile | 9 | ||||
| -rw-r--r-- | railties/guides/source/configuring.textile | 18 | ||||
| -rw-r--r-- | railties/guides/source/engines.textile | 36 | ||||
| -rw-r--r-- | railties/guides/source/getting_started.textile | 124 | ||||
| -rw-r--r-- | railties/guides/source/migrations.textile | 62 |
8 files changed, 244 insertions, 185 deletions
diff --git a/railties/guides/source/active_record_basics.textile b/railties/guides/source/active_record_basics.textile index cab8c80866..66ad7b0255 100644 --- a/railties/guides/source/active_record_basics.textile +++ b/railties/guides/source/active_record_basics.textile @@ -38,47 +38,48 @@ When writing applications using other programming languages or frameworks, it ma h4. Naming Conventions -By default, Active Record uses some naming conventions to find out how the mapping between models and database tables should be created. Rails will pluralize your class names to find the respective database table. So, for a class +Book+, you should have a database table called *books*. The Rails pluralization mechanisms are very powerful, being capable to pluralize (and singularize) both regular and irregular words. When using class names composed of two or more words, the model class name should follow the Ruby conventions, using the camelCase form, while the table name must contain the words separated by underscores. Examples: +By default, Active Record uses some naming conventions to find out how the mapping between models and database tables should be created. Rails will pluralize your class names to find the respective database table. So, for a class +Book+, you should have a database table called *books*. The Rails pluralization mechanisms are very powerful, being capable to pluralize (and singularize) both regular and irregular words. When using class names composed of two or more words, the model class name should follow the Ruby conventions, using the CamelCase form, while the table name must contain the words separated by underscores. Examples: -* Database Table - Plural with underscores separating words (e.g., book_clubs) -* Model Class - Singular with the first letter of each word capitalized (e.g., BookClub) +* Database Table - Plural with underscores separating words (e.g., +book_clubs+) +* Model Class - Singular with the first letter of each word capitalized (e.g., +BookClub+) |_.Model / Class |_.Table / Schema | -|Post |posts| -|LineItem |line_items| -|Deer |deer| -|Mouse |mice| -|Person |people| +|+Post+ |+posts+| +|+LineItem+ |+line_items+| +|+Deer+ |+deer+| +|+Mouse+ |+mice+| +|+Person+ |+people+| h4. Schema Conventions Active Record uses naming conventions for the columns in database tables, depending on the purpose of these columns. -* *Foreign keys* - These fields should be named following the pattern table_id (e.g., item_id, order_id). These are the fields that Active Record will look for when you create associations between your models. -* *Primary keys* - By default, Active Record will use an integer column named "id" as the table's primary key. When using "Rails Migrations":migrations.html to create your tables, this column will be automatically created. +* *Foreign keys* - These fields should be named following the pattern +singularized_table_name_id+ (e.g., +item_id+, +order_id+). These are the fields that Active Record will look for when you create associations between your models. +* *Primary keys* - By default, Active Record will use an integer column named +id+ as the table's primary key. When using "Rails Migrations":migrations.html to create your tables, this column will be automatically created. There are also some optional column names that will create additional features to Active Record instances: -* *created_at* - Automatically gets set to the current date and time when the record is first created. -* *created_on* - Automatically gets set to the current date when the record is first created. -* *updated_at* - Automatically gets set to the current date and time whenever the record is updated. -* *updated_on* - Automatically gets set to the current date whenever the record is updated. -* *lock_version* - Adds "optimistic locking":http://api.rubyonrails.org/classes/ActiveRecord/Locking.html to a model. -* *type* - Specifies that the model uses "Single Table Inheritance":http://api.rubyonrails.org/classes/ActiveRecord/Base.html -* *(table_name)_count* - Used to cache the number of belonging objects on associations. For example, a +comments_count+ column in a +Post+ class that has many instances of +Comment+ will cache the number of existent comments for each post. +* +created_at+ - Automatically gets set to the current date and time when the record is first created. +* +created_on+ - Automatically gets set to the current date when the record is first created. +* +updated_at+ - Automatically gets set to the current date and time whenever the record is updated. +* +updated_on+ - Automatically gets set to the current date whenever the record is updated. +* +lock_version+ - Adds "optimistic locking":http://api.rubyonrails.org/classes/ActiveRecord/Locking.html to a model. +* +type+ - Specifies that the model uses "Single Table Inheritance":http://api.rubyonrails.org/classes/ActiveRecord/Base.html +* +(table_name)_count+ - Used to cache the number of belonging objects on associations. For example, a +comments_count+ column in a +Post+ class that has many instances of +Comment+ will cache the number of existent comments for each post. -NOTE: While these column names are optional they are in fact reserved by Active Record. Steer clear of reserved keywords unless you want the extra functionality. For example, "type" is a reserved keyword used to designate a table using Single Table Inheritance. If you are not using STI, try an analogous keyword like "context", that may still accurately describe the data you are modeling. +NOTE: While these column names are optional, they are in fact reserved by Active Record. Steer clear of reserved keywords unless you want the extra functionality. For example, +type+ is a reserved keyword used to designate a table using Single Table Inheritance (STI). If you are not using STI, try an analogous keyword like "context", that may still accurately describe the data you are modeling. h3. Creating Active Record Models -It's very easy to create Active Record models. All you have to do is to subclass the +ActiveRecord::Base+ class and you're good to go: +It is very easy to create Active Record models. All you have to do is to subclass the +ActiveRecord::Base+ class and you're good to go: <ruby> -class Product < ActiveRecord::Base; end +class Product < ActiveRecord::Base +end </ruby> -This will create a +Product+ model, mapped to a *products* table at the database. By doing this you'll also have the ability to map the columns of each row in that table with the attributes of the instances of your model. So, suppose that the *products* table was created using an SQL sentence like: +This will create a +Product+ model, mapped to a +products+ table at the database. By doing this you'll also have the ability to map the columns of each row in that table with the attributes of the instances of your model. Suppose that the +products+ table was created using an SQL sentence like: <sql> CREATE TABLE products ( @@ -126,21 +127,21 @@ class Product < ActiveRecord::Base end </ruby> -h3. Reading and Writing Data +h3. CRUD: Reading and Writing Data CRUD is an acronym for the four verbs we use to operate on data: *C*reate, *R*ead, *U*pdate and *D*elete. Active Record automatically creates methods to allow an application to read and manipulate data stored within its tables. h4. Create -Active Record objects can be created from a hash, a block or have its attributes manually set after creation. The _new_ method will return a new object while _create_ will return the object and save it to the database. +Active Record objects can be created from a hash, a block or have their attributes manually set after creation. The +new+ method will return a new object while +create+ will return the object and save it to the database. -For example, given a model +User+ with attributes of +name+ and +occupation+, the _create_ method call will create and save a new record into the database: +For example, given a model +User+ with attributes of +name+ and +occupation+, the +create+ method call will create and save a new record into the database: <ruby> user = User.create(:name => "David", :occupation => "Code Artist") </ruby> -Using the _new_ method, an object can be created without being saved: +Using the +new+ method, an object can be created without being saved: <ruby> user = User.new @@ -148,9 +149,9 @@ Using the _new_ method, an object can be created without being saved: user.occupation = "Code Artist" </ruby> -A call to _user.save_ will commit the record to the database. +A call to +user.save+ will commit the record to the database. -Finally, passing a block to either create or new will return a new User object: +Finally, if a block is provided, both +create+ and +new+ will yield the new object to that block for initialization: <ruby> user = User.new do |u| @@ -164,7 +165,7 @@ h4. Read Active Record provides a rich API for accessing data within a database. Below are a few examples of different data access methods provided by Active Record. <ruby> - # return all records + # return array with all records users = User.all </ruby> diff --git a/railties/guides/source/active_record_querying.textile b/railties/guides/source/active_record_querying.textile index 96f91cfef6..b1acdd189a 100644 --- a/railties/guides/source/active_record_querying.textile +++ b/railties/guides/source/active_record_querying.textile @@ -616,7 +616,7 @@ c1.first_name = "Michael" c1.save c2.name = "should fail" -c2.save # Raises a ActiveRecord::StaleObjectError +c2.save # Raises an ActiveRecord::StaleObjectError </ruby> You're then responsible for dealing with the conflict by rescuing the exception and either rolling back, merging, or otherwise apply the business logic needed to resolve the conflict. diff --git a/railties/guides/source/active_record_validations_callbacks.textile b/railties/guides/source/active_record_validations_callbacks.textile index 5c3aae2955..2a1e9bfc0c 100644 --- a/railties/guides/source/active_record_validations_callbacks.textile +++ b/railties/guides/source/active_record_validations_callbacks.textile @@ -28,7 +28,7 @@ h4. Why Use Validations? Validations are used to ensure that only valid data is saved into your database. For example, it may be important to your application to ensure that every user provides a valid email address and mailing address. -There are several ways to validate data before it is saved into your database, including native database constraints, client-side validations, controller-level validations, and model-level validations. +There are several ways to validate data before it is saved into your database, including native database constraints, client-side validations, controller-level validations, and model-level validations: * Database constraints and/or stored procedures make the validation mechanisms database-dependent and can make testing and maintenance more difficult. However, if your database is used by other applications, it may be a good idea to use some constraints at the database level. Additionally, database-level validations can safely handle some things (such as uniqueness in heavily-used tables) that can be difficult to implement otherwise. * Client-side validations can be useful, but are generally unreliable if used alone. If they are implemented using JavaScript, they may be bypassed if JavaScript is turned off in the user's browser. However, if combined with other techniques, client-side validation can be a convenient way to provide users with immediate feedback as they use your site. @@ -94,7 +94,7 @@ Note that +save+ also has the ability to skip validations if passed +:validate = h4. +valid?+ and +invalid?+ -To verify whether or not an object is valid, Rails uses the +valid?+ method. You can also use this method on your own. +valid?+ triggers your validations and returns true if no errors were added to the object, and false otherwise. +To verify whether or not an object is valid, Rails uses the +valid?+ method. You can also use this method on your own. +valid?+ triggers your validations and returns true if no errors were found in the object, and false otherwise. <ruby> class Person < ActiveRecord::Base @@ -105,7 +105,7 @@ Person.create(:name => "John Doe").valid? # => true Person.create(:name => nil).valid? # => false </ruby> -When Active Record is performing validations, any errors found can be accessed through the +errors+ instance method. By definition an object is valid if this collection is empty after running validations. +After Active Record has performed validations, any errors found can be accessed through the +errors+ instance method, which returns a collection of errors. By definition, an object is valid if this collection is empty after running validations. Note that an object instantiated with +new+ will not report errors even if it's technically invalid, because validations are not run when using +new+. @@ -139,7 +139,7 @@ end => ActiveRecord::RecordInvalid: Validation failed: Name can't be blank </ruby> -+invalid?+ is simply the inverse of +valid?+. +invalid?+ triggers your validations and returns true if any errors were added to the object, and false otherwise. ++invalid?+ is simply the inverse of +valid?+. +invalid?+ triggers your validations, returning true if any errors were found in the object, and false otherwise. h4(#validations_overview-errors). +errors[]+ @@ -160,7 +160,7 @@ We'll cover validation errors in greater depth in the "Working with Validation E h3. Validation Helpers -Active Record offers many pre-defined validation helpers that you can use directly inside your class definitions. These helpers provide common validation rules. Every time a validation fails, an error message is added to the object's +errors+ collection, and this message is associated with the field being validated. +Active Record offers many pre-defined validation helpers that you can use directly inside your class definitions. These helpers provide common validation rules. Every time a validation fails, an error message is added to the object's +errors+ collection, and this message is associated with the attribute being validated. Each helper accepts an arbitrary number of attribute names, so with a single line of code you can add the same kind of validation to several attributes. @@ -428,6 +428,8 @@ class GoodnessValidator < ActiveModel::Validator end </ruby> +NOTE: Errors added to +record.errors[:base]+ relate to the state of the record as a whole, and not to a specific attribute. + The +validates_with+ helper takes a class, or a list of classes to use for validation. There is no default error message for +validates_with+. You must manually add errors to the record's errors collection in the validator class. To implement the validate method, you must have a +record+ parameter defined, which is the record to be validated. @@ -454,13 +456,13 @@ This helper validates attributes against a block. It doesn't have a predefined v <ruby> class Person < ActiveRecord::Base - validates_each :name, :surname do |model, attr, value| - model.errors.add(attr, 'must start with upper case') if value =~ /\A[a-z]/ + validates_each :name, :surname do |record, attr, value| + record.errors.add(attr, 'must start with upper case') if value =~ /\A[a-z]/ end end </ruby> -The block receives the model, the attribute's name and the attribute's value. You can do anything you like to check for valid data within the block. If your validation fails, you can add an error message to the model, therefore making it invalid. +The block receives the record, the attribute's name and the attribute's value. You can do anything you like to check for valid data within the block. If your validation fails, you should add an error message to the model, therefore making it invalid. h3. Common Validation Options @@ -580,7 +582,7 @@ Custom validators are classes that extend <tt>ActiveModel::Validator</tt>. These <ruby> class MyValidator < ActiveModel::Validator def validate(record) - if record.name.starts_with? 'X' + unless record.name.starts_with? 'X' record.errors[:name] << 'Need a name starting with X please!' end end @@ -661,7 +663,7 @@ The following is a list of the most commonly used methods. Please refer to the + h4(#working_with_validation_errors-errors). +errors+ -Returns an OrderedHash with all errors. Each key is the attribute name and the value is an array of strings with all errors. +Returns an instance of the class +ActiveModel::Errors+ (which behaves like an ordered hash) containing all errors. Each key is the attribute name and the value is an array of strings with all errors. <ruby> class Person < ActiveRecord::Base @@ -741,7 +743,7 @@ Another way to do this is using +[]=+ setter h4. +errors[:base]+ -You can add error messages that are related to the object's state as a whole, instead of being related to a specific attribute. You can use this method when you want to say that the object is invalid, no matter the values of its attributes. Since +errors[:base]+ is an array, you can simply add a string to the array and uses it as the error message. +You can add error messages that are related to the object's state as a whole, instead of being related to a specific attribute. You can use this method when you want to say that the object is invalid, no matter the values of its attributes. Since +errors[:base]+ is an array, you can simply add a string to it and it will be used as an error message. <ruby> class Person < ActiveRecord::Base @@ -785,7 +787,7 @@ end person = Person.new person.valid? # => false -person.errors.size # => 3 +person.errors.size # => 2 person = Person.new(:name => "Andrea", :email => "andrea@example.com") person.valid? # => true @@ -794,7 +796,7 @@ person.errors.size # => 0 h3. Displaying Validation Errors in the View -Rails maintains an official plugin that provides helpers to display the error messages of your models in your view templates. You can install it as a plugin or as a Gem. +Rails maintains an official plugin, DynamicForm, that provides helpers to display the error messages of your models in your view templates. You can install it as a plugin or as a Gem. h4. Installing as a plugin @@ -810,7 +812,7 @@ Add this line in your Gemfile: gem "dynamic_form" </ruby> -Now you will have access to these two methods in your view templates. +Now you will have access to the two helper methods +error_messages+ and +error_messages_for+ in your view templates. h4. +error_messages+ and +error_messages_for+ @@ -840,11 +842,13 @@ end <% end %> </erb> -To get the idea, if you submit the form with empty fields you typically get this back, though styles are indeed missing by default: +If you submit the form with empty fields, the result will be similar to the one shown below: !images/error_messages.png(Error messages)! -You can also use the +error_messages_for+ helper to display the error messages of a model assigned to a view template. It's very similar to the previous example and will achieve exactly the same result. +NOTE: The appearance of the generated HTML will be different from the one shown, unless you have used scaffolding. See "Customizing the Error Messages CSS":#customizing-error-messages-css. + +You can also use the +error_messages_for+ helper to display the error messages of a model assigned to a view template. It is very similar to the previous example and will achieve exactly the same result. <erb> <%= error_messages_for :product %> @@ -852,7 +856,7 @@ You can also use the +error_messages_for+ helper to display the error messages o The displayed text for each error message will always be formed by the capitalized name of the attribute that holds the error, followed by the error message itself. -Both the +form.error_messages+ and the +error_messages_for+ helpers accept options that let you customize the +div+ element that holds the messages, changing the header text, the message below the header text and the tag used for the element that defines the header. +Both the +form.error_messages+ and the +error_messages_for+ helpers accept options that let you customize the +div+ element that holds the messages, change the header text, change the message below the header, and specify the tag used for the header element. For example, <erb> <%= f.error_messages :header_message => "Invalid product!", @@ -860,23 +864,23 @@ Both the +form.error_messages+ and the +error_messages_for+ helpers accept optio :header_tag => :h3 %> </erb> -Which results in the following content: +results in: !images/customized_error_messages.png(Customized error messages)! -If you pass +nil+ to any of these options, it will get rid of the respective section of the +div+. +If you pass +nil+ in any of these options, the corresponding section of the +div+ will be discarded. -h4. Customizing the Error Messages CSS +h4(#customizing-error-messages-css). Customizing the Error Messages CSS -The selectors to customize the style of error messages are: +The selectors used to customize the style of error messages are: * +.field_with_errors+ - Style for the form fields and labels with errors. -* +#errorExplanation+ - Style for the +div+ element with the error messages. -* +#errorExplanation h2+ - Style for the header of the +div+ element. -* +#errorExplanation p+ - Style for the paragraph that holds the message that appears right below the header of the +div+ element. -* +#errorExplanation ul li+ - Style for the list items with individual error messages. +* +#error_explanation+ - Style for the +div+ element with the error messages. +* +#error_explanation h2+ - Style for the header of the +div+ element. +* +#error_explanation p+ - Style for the paragraph holding the message that appears right below the header of the +div+ element. +* +#error_explanation ul li+ - Style for the list items with individual error messages. -Scaffolding for example generates +app/assets/stylesheets/scaffold.css.scss+, which later compiles to +app/assets/stylesheets/scaffold.css+ and defines the red-based style you saw above. +If scaffolding was used, file +app/assets/stylesheets/scaffold.css.scss+ (which later compiles to +app/assets/stylesheets/scaffold.css+), will have been generated automatically. This file defines the red-based styles you saw in the examples above. The name of the class and the id can be changed with the +:class+ and +:id+ options, accepted by both helpers. @@ -889,7 +893,7 @@ The way form fields with errors are treated is defined by +ActionView::Base.fiel * A string with the HTML tag * An instance of +ActionView::Helpers::InstanceTag+. -Here is a simple example where we change the Rails behavior to always display the error messages in front of each of the form fields with errors. The error messages will be enclosed by a +span+ element with a +validation-error+ CSS class. There will be no +div+ element enclosing the +input+ element, so we get rid of that red border around the text field. You can use the +validation-error+ CSS class to style it anyway you want. +Below is a simple example where we change the Rails behavior to always display the error messages in front of each of the form fields in error. The error messages will be enclosed by a +span+ element with a +validation-error+ CSS class. There will be no +div+ element enclosing the +input+ element, so we get rid of that red border around the text field. You can use the +validation-error+ CSS class to style it anyway you want. <ruby> ActionView::Base.field_error_proc = Proc.new do |html_tag, instance| @@ -903,17 +907,17 @@ ActionView::Base.field_error_proc = Proc.new do |html_tag, instance| end </ruby> -This will result in something like the following: +The result looks like the following: !images/validation_error_messages.png(Validation error messages)! h3. Callbacks Overview -Callbacks are methods that get called at certain moments of an object's life cycle. With callbacks it's possible to write code that will run whenever an Active Record object is created, saved, updated, deleted, validated, or loaded from the database. +Callbacks are methods that get called at certain moments of an object's life cycle. With callbacks it is possible to write code that will run whenever an Active Record object is created, saved, updated, deleted, validated, or loaded from the database. h4. Callback Registration -In order to use the available callbacks, you need to register them. You can do that by implementing them as ordinary methods, and then using a macro-style class method to register them as callbacks. +In order to use the available callbacks, you need to register them. You can implement the callbacks as ordinary methods and use a macro-style class method to register them as callbacks: <ruby> class User < ActiveRecord::Base @@ -930,7 +934,7 @@ class User < ActiveRecord::Base end </ruby> -The macro-style class methods can also receive a block. Consider using this style if the code inside your block is so short that it fits in just one line. +The macro-style class methods can also receive a block. Consider using this style if the code inside your block is so short that it fits in a single line: <ruby> class User < ActiveRecord::Base @@ -942,7 +946,7 @@ class User < ActiveRecord::Base end </ruby> -It's considered good practice to declare callback methods as being protected or private. If left public, they can be called from outside of the model and violate the principle of object encapsulation. +It is considered good practice to declare callback methods as protected or private. If left public, they can be called from outside of the model and violate the principle of object encapsulation. h3. Available Callbacks @@ -982,7 +986,7 @@ The +after_initialize+ callback will be called whenever an Active Record object The +after_find+ callback will be called whenever Active Record loads a record from the database. +after_find+ is called before +after_initialize+ if both are defined. -The +after_initialize+ and +after_find+ callbacks are a bit different from the others. They have no +before_*+ counterparts, and the only way to register them is by defining them as regular methods. If you try to register +after_initialize+ or +after_find+ using macro-style class methods, they will just be ignored. This behavior is due to performance reasons, since +after_initialize+ and +after_find+ will both be called for each record found in the database, significantly slowing down the queries. +The +after_initialize+ and +after_find+ callbacks are a bit different from the others. They have no +before_*+ counterparts, and they are registered simply by defining them as regular methods with predefined names. If you try to register +after_initialize+ or +after_find+ using macro-style class methods, they will just be ignored. This behavior is due to performance reasons, since +after_initialize+ and +after_find+ will both be called for each record found in the database, which would otherwise significantly slow down the queries. <ruby> class User < ActiveRecord::Base @@ -1039,7 +1043,7 @@ The +after_initialize+ callback is triggered every time a new object of the clas h3. Skipping Callbacks -Just as with validations, it's also possible to skip callbacks. These methods should be used with caution, however, because important business rules and application logic may be kept in callbacks. Bypassing them without understanding the potential implications may lead to invalid data. +Just as with validations, it is also possible to skip callbacks. These methods should be used with caution, however, because important business rules and application logic may be kept in callbacks. Bypassing them without understanding the potential implications may lead to invalid data. * +decrement+ * +decrement_counter+ @@ -1058,13 +1062,13 @@ h3. Halting Execution As you start registering new callbacks for your models, they will be queued for execution. This queue will include all your model's validations, the registered callbacks, and the database operation to be executed. -The whole callback chain is wrapped in a transaction. If any <em>before</em> callback method returns exactly +false+ or raises an exception the execution chain gets halted and a ROLLBACK is issued; <em>after</em> callbacks can only accomplish that by raising an exception. +The whole callback chain is wrapped in a transaction. If any <em>before</em> callback method returns exactly +false+ or raises an exception, the execution chain gets halted and a ROLLBACK is issued; <em>after</em> callbacks can only accomplish that by raising an exception. -WARNING. Raising an arbitrary exception may break code that expects +save+ and friends not to fail like that. The +ActiveRecord::Rollback+ exception is thought precisely to tell Active Record a rollback is going on. That one is internally captured but not reraised. +WARNING. Raising an arbitrary exception may break code that expects +save+ and its friends not to fail like that. The +ActiveRecord::Rollback+ exception is thought precisely to tell Active Record a rollback is going on. That one is internally captured but not reraised. h3. Relational Callbacks -Callbacks work through model relationships, and can even be defined by them. Let's take an example where a user has many posts. In our example, a user's posts should be destroyed if the user is destroyed. So, we'll add an +after_destroy+ callback to the +User+ model by way of its relationship to the +Post+ model. +Callbacks work through model relationships, and can even be defined by them. Suppose an example where a user has many posts. A user's posts should be destroyed if the user is destroyed. Let's add an +after_destroy+ callback to the +User+ model by way of its relationship to the +Post+ model: <ruby> class User < ActiveRecord::Base @@ -1090,11 +1094,11 @@ Post destroyed h3. Conditional Callbacks -Like in validations, we can also make our callbacks conditional, calling them only when a given predicate is satisfied. You can do that by using the +:if+ and +:unless+ options, which can take a symbol, a string or a +Proc+. You may use the +:if+ option when you want to specify when the callback *should* get called. If you want to specify when the callback *should not* be called, then you may use the +:unless+ option. +As with validations, we can also make the calling of a callback method conditional on the satisfaction of a given predicate. We can do this using the +:if+ and +:unless+ options, which can take a symbol, a string or a +Proc+. You may use the +:if+ option when you want to specify under which conditions the callback *should* be called. If you want to specify the conditions under which the callback *should not* be called, then you may use the +:unless+ option. -h4. Using +:if+ and +:unless+ with a Symbol +h4. Using +:if+ and +:unless+ with a +Symbol+ -You can associate the +:if+ and +:unless+ options with a symbol corresponding to the name of a method that will get called right before the callback. When using the +:if+ option, the callback won't be executed if the method returns false; when using the +:unless+ option, the callback won't be executed if the method returns true. This is the most common option. Using this form of registration it's also possible to register several different methods that should be called to check if the callback should be executed. +You can associate the +:if+ and +:unless+ options with a symbol corresponding to the name of a predicate method that will get called right before the callback. When using the +:if+ option, the callback won't be executed if the predicate method returns false; when using the +:unless+ option, the callback won't be executed if the predicate method returns true. This is the most common option. Using this form of registration it is also possible to register several different predicates that should be called to check if the callback should be executed. <ruby> class Order < ActiveRecord::Base @@ -1104,7 +1108,7 @@ end h4. Using +:if+ and +:unless+ with a String -You can also use a string that will be evaluated using +eval+ and needs to contain valid Ruby code. You should use this option only when the string represents a really short condition. +You can also use a string that will be evaluated using +eval+ and hence needs to contain valid Ruby code. You should use this option only when the string represents a really short condition: <ruby> class Order < ActiveRecord::Base @@ -1112,9 +1116,9 @@ class Order < ActiveRecord::Base end </ruby> -h4. Using +:if+ and +:unless+ with a Proc +h4. Using +:if+ and +:unless+ with a +Proc+ -Finally, it's possible to associate +:if+ and +:unless+ with a +Proc+ object. This option is best suited when writing short validation methods, usually one-liners. +Finally, it is possible to associate +:if+ and +:unless+ with a +Proc+ object. This option is best suited when writing short validation methods, usually one-liners: <ruby> class Order < ActiveRecord::Base @@ -1125,7 +1129,7 @@ end h4. Multiple Conditions for Callbacks -When writing conditional callbacks, it's possible to mix both +:if+ and +:unless+ in the same callback declaration. +When writing conditional callbacks, it is possible to mix both +:if+ and +:unless+ in the same callback declaration: <ruby> class Comment < ActiveRecord::Base @@ -1138,7 +1142,7 @@ h3. Callback Classes Sometimes the callback methods that you'll write will be useful enough to be reused by other models. Active Record makes it possible to create classes that encapsulate the callback methods, so it becomes very easy to reuse them. -Here's an example where we create a class with an +after_destroy+ callback for a +PictureFile+ model. +Here's an example where we create a class with an +after_destroy+ callback for a +PictureFile+ model: <ruby> class PictureFileCallbacks @@ -1150,7 +1154,7 @@ class PictureFileCallbacks end </ruby> -When declared inside a class the callback method will receive the model object as a parameter. We can now use it this way: +When declared inside a class, as above, the callback methods will receive the model object as a parameter. We can now use the callback class in the model: <ruby> class PictureFile < ActiveRecord::Base @@ -1158,7 +1162,7 @@ class PictureFile < ActiveRecord::Base end </ruby> -Note that we needed to instantiate a new +PictureFileCallbacks+ object, since we declared our callback as an instance method. Sometimes it will make more sense to have it as a class method. +Note that we needed to instantiate a new +PictureFileCallbacks+ object, since we declared our callback as an instance method. This is particularly useful if the callbacks make use of the state of instantiated object. Often, however, it will make more sense to declare the callbacks as class methods: <ruby> class PictureFileCallbacks @@ -1182,16 +1186,25 @@ You can declare as many callbacks as you want inside your callback classes. h3. Observers -Observers are similar to callbacks, but with important differences. Whereas callbacks can pollute a model with code that isn't directly related to its purpose, observers allow you to add the same functionality outside of a model. For example, it could be argued that a +User+ model should not include code to send registration confirmation emails. Whenever you use callbacks with code that isn't directly related to your model, you may want to consider creating an observer instead. +Observers are similar to callbacks, but with important differences. Whereas callbacks can pollute a model with code that isn't directly related to its purpose, observers allow you to add the same functionality without changing the code of the model. For example, it could be argued that a +User+ model should not include code to send registration confirmation emails. Whenever you use callbacks with code that isn't directly related to your model, you may want to consider creating an observer instead. h4. Creating Observers -For example, imagine a +User+ model where we want to send an email every time a new user is created. Because sending emails is not directly related to our model's purpose, we could create an observer to contain this functionality. +For example, imagine a +User+ model where we want to send an email every time a new user is created. Because sending emails is not directly related to our model's purpose, we should create an observer to contain the code implementing this functionality. <shell> $ rails generate observer User </shell> +generates +app/models/user_observer.rb+ containing the observer class +UserObserver+: + +<ruby> +class UserObserver < ActiveRecord::Observer +end +</ruby> + +You may now add methods to be called at the desired occasions: + <ruby> class UserObserver < ActiveRecord::Observer def after_create(model) @@ -1207,7 +1220,7 @@ h4. Registering Observers Observers are conventionally placed inside of your +app/models+ directory and registered in your application's +config/application.rb+ file. For example, the +UserObserver+ above would be saved as +app/models/user_observer.rb+ and registered in +config/application.rb+ this way: <ruby> -# Activate observers that should always be running +# Activate observers that should always be running. config.active_record.observers = :user_observer </ruby> @@ -1215,7 +1228,7 @@ As usual, settings in +config/environments+ take precedence over those in +confi h4. Sharing Observers -By default, Rails will simply strip "Observer" from an observer's name to find the model it should observe. However, observers can also be used to add behavior to more than one model, and so it's possible to manually specify the models that our observer should observe. +By default, Rails will simply strip "Observer" from an observer's name to find the model it should observe. However, observers can also be used to add behavior to more than one model, and thus it is possible to explicitly specify the models that our observer should observe: <ruby> class MailerObserver < ActiveRecord::Observer @@ -1227,10 +1240,10 @@ class MailerObserver < ActiveRecord::Observer end </ruby> -In this example, the +after_create+ method would be called whenever a +Registration+ or +User+ was created. Note that this new +MailerObserver+ would also need to be registered in +config/application.rb+ in order to take effect. +In this example, the +after_create+ method will be called whenever a +Registration+ or +User+ is created. Note that this new +MailerObserver+ would also need to be registered in +config/application.rb+ in order to take effect: <ruby> -# Activate observers that should always be running +# Activate observers that should always be running. config.active_record.observers = :mailer_observer </ruby> @@ -1238,7 +1251,7 @@ h3. Transaction Callbacks There are two additional callbacks that are triggered by the completion of a database transaction: +after_commit+ and +after_rollback+. These callbacks are very similar to the +after_save+ callback except that they don't execute until after database changes have either been committed or rolled back. They are most useful when your active record models need to interact with external systems which are not part of the database transaction. -Consider, for example, the previous example where the +PictureFile+ model needs to delete a file after a record is destroyed. If anything raises an exception after the +after_destroy+ callback is called and the transaction rolls back, the file will have been deleted and the model will be left in an inconsistent state. For example, suppose that +picture_file_2+ in the code below is not valid and the +save!+ method raises an error. +Consider, for example, the previous example where the +PictureFile+ model needs to delete a file after the corresponding record is destroyed. If anything raises an exception after the +after_destroy+ callback is called and the transaction rolls back, the file will have been deleted and the model will be left in an inconsistent state. For example, suppose that +picture_file_2+ in the code below is not valid and the +save!+ method raises an error. <ruby> PictureFile.transaction do diff --git a/railties/guides/source/asset_pipeline.textile b/railties/guides/source/asset_pipeline.textile index a0af018d30..7795b297f3 100644 --- a/railties/guides/source/asset_pipeline.textile +++ b/railties/guides/source/asset_pipeline.textile @@ -346,6 +346,15 @@ The rake task is: bundle exec rake assets:precompile </plain> +For faster asset precompiles, you can partially load your application by setting ++config.assets.initialize_on_precompile+ to false, though in that case templates +cannot see application objects or methods. *Heroku requires this to be false.* + +WARNING: If you set +config.assets.initialize_on_precompile+ to false, be sure to +test +rake assets:precompile+ locally before deploying. It may expose bugs where +your assets reference application objects or methods, since those are still +in scope in development mode regardless of the value of this flag. + Capistrano (v2.8.0 and above) has a recipe to handle this in deployment. Add the following line to +Capfile+: <erb> diff --git a/railties/guides/source/configuring.textile b/railties/guides/source/configuring.textile index 41b53440f7..ce1d759d5b 100644 --- a/railties/guides/source/configuring.textile +++ b/railties/guides/source/configuring.textile @@ -179,16 +179,16 @@ h4. Configuring Middleware Every Rails application comes with a standard set of middleware which it uses in this order in the development environment: -* +Rack::SSL+ Will force every request to be under HTTPS protocol. Will be available if +config.force_ssl+ is set to +true+. Options passed to this can be configured by using +config.ssl_options+. +* +Rack::SSL+ forces every request to be under HTTPS protocol. Will be available if +config.force_ssl+ is set to +true+. Options passed to this can be configured by using +config.ssl_options+. * +ActionDispatch::Static+ is used to serve static assets. Disabled if +config.serve_static_assets+ is +true+. -* +Rack::Lock+ Will wrap the app in mutex so it can only be called by a single thread at a time. Only enabled if +config.action_controller.allow_concurrency+ is set to +false+, which it is by default. -* +ActiveSupport::Cache::Strategy::LocalCache+ Serves as a basic memory backed cache. This cache is not thread safe and is intended only for serving as a temporary memory cache for a single thread. -* +Rack::Runtime+ Sets an +X-Runtime+ header, containing the time (in seconds) taken to execute the request. -* +Rails::Rack::Logger+ Notifies the logs that the request has began. After request is complete, flushes all the logs. -* +ActionDispatch::ShowExceptions+ Rescues any exception returned by the application and renders nice exception pages if the request is local or if +config.consider_all_requests_local+ is set to +true+. If +config.action_dispatch.show_exceptions+ is set to +false+, exceptions will be raised regardless. -* +ActionDispatch::RemoteIp+ Checks for IP spoofing attacks. Configurable with the +config.action_dispatch.ip_spoofing_check+ and +config.action_dispatch.trusted_proxies+ settings. -* +Rack::Sendfile+ Intercepts responses whose body is being served from a file and replaces it with a server specific X-Sendfile header. Configurable with +config.action_dispatch.x_sendfile_header+. -* +ActionDispatch::Callbacks+ Runs the prepare callbacks before serving the request. +* +Rack::Lock+ wraps the app in mutex so it can only be called by a single thread at a time. Only enabled if +config.action_controller.allow_concurrency+ is set to +false+, which it is by default. +* +ActiveSupport::Cache::Strategy::LocalCache+ serves as a basic memory backed cache. This cache is not thread safe and is intended only for serving as a temporary memory cache for a single thread. +* +Rack::Runtime+ sets an +X-Runtime+ header, containing the time (in seconds) taken to execute the request. +* +Rails::Rack::Logger+ notifies the logs that the request has began. After request is complete, flushes all the logs. +* +ActionDispatch::ShowExceptions+ rescues any exception returned by the application and renders nice exception pages if the request is local or if +config.consider_all_requests_local+ is set to +true+. If +config.action_dispatch.show_exceptions+ is set to +false+, exceptions will be raised regardless. +* +ActionDispatch::RemoteIp+ checks for IP spoofing attacks. Configurable with the +config.action_dispatch.ip_spoofing_check+ and +config.action_dispatch.trusted_proxies+ settings. +* +Rack::Sendfile+ intercepts responses whose body is being served from a file and replaces it with a server specific X-Sendfile header. Configurable with +config.action_dispatch.x_sendfile_header+. +* +ActionDispatch::Callbacks+ runs the prepare callbacks before serving the request. * +ActiveRecord::ConnectionAdapters::ConnectionManagement+ cleans active connections after each request, unless the +rack.test+ key in the request environment is set to +true+. * +ActiveRecord::QueryCache+ caches all SELECT queries generated in a request. If any INSERT or UPDATE takes place then the cache is cleaned. * +ActionDispatch::Cookies+ sets cookies for the request. diff --git a/railties/guides/source/engines.textile b/railties/guides/source/engines.textile new file mode 100644 index 0000000000..dc87ac4095 --- /dev/null +++ b/railties/guides/source/engines.textile @@ -0,0 +1,36 @@ +h2. Getting Started with Engines + +In this guide you will learn about engines and how they can be used to provide additional functionality to their host applications through a clean and very easy-to-use interface. You will learn the following things in this guide: + +* What are engines +* Generating an engine +* Building features for the engine +* Hooking the engine into an application +* Overriding engine functionality in the application + +endprologue. + +h3. What are engines? + +Engines can be considered miniature applications that provide functionality to their host applications. A Rails application is actually just a "supercharged" engine, with the `Rails::Application` class inheriting from `Rails::Engine`. Therefore, engines and applications share common functionality but are at the same time two separate beasts. + +h3. Generating an engine + +TODO: The engine that will be generated for this guide will be called "blorgh". It's a blogging engine that provides posts and comments and that's it. + +TODO: Describe here the process of generating an engine and what an engine comes with. + +h3. Providing engine functionality + +TODO: Brief explanation of what this engine is going to be doing and what we will have once we are done. +TODO: Generate a posts scaffold (maybe?) for the engine +TODO: Generate a comments scaffold (maybe?) for the engine + +h3. Hooking into application + +TODO: Application will provide a User foundation class which the engine hooks into through a configuration setting, configurable in the application's initializers. The engine will be mounted at the +/blog+ path in the application. + +h3. Overriding engine functionality + +TODO: Cover how to override engine functionality in the engine, such as controllers and views. +IDEA: I like Devise's +devise :controllers => { "sessions" => "sessions" }+ idea. Perhaps we could incorporate that into the guide?
\ No newline at end of file diff --git a/railties/guides/source/getting_started.textile b/railties/guides/source/getting_started.textile index 33f383f173..bf6104b96b 100644 --- a/railties/guides/source/getting_started.textile +++ b/railties/guides/source/getting_started.textile @@ -360,7 +360,7 @@ development: h5. Configuring an SQLite3 Database for JRuby Platform -If you choose to use SQLite3 and using JRuby, your +config/database.yml+ will +If you choose to use SQLite3 and are using JRuby, your +config/database.yml+ will look a little different. Here's the development section: <yaml> @@ -371,7 +371,7 @@ development: h5. Configuring a MySQL Database for JRuby Platform -If you choose to use MySQL and using JRuby, your +config/database.yml+ will look +If you choose to use MySQL and are using JRuby, your +config/database.yml+ will look a little different. Here's the development section: <yaml> @@ -384,7 +384,7 @@ development: h5. Configuring a PostgreSQL Database for JRuby Platform -Finally if you choose to use PostgreSQL and using JRuby, your +Finally if you choose to use PostgreSQL and are using JRuby, your +config/database.yml+ will look a little different. Here's the development section: @@ -599,7 +599,7 @@ The above migration creates a method named +change+ which will be called when yo run this migration. The action defined in that method is also reversible, which means Rails knows how to reverse the change made by this migration, in case you want to reverse it at later date. By default, when you run this migration it -will creates a +posts+ table with two string columns and a text column. It also +creates a +posts+ table with two string columns and a text column. It also creates two timestamp fields to track record creation and updating. More information about Rails migrations can be found in the "Rails Database Migrations":migrations.html guide. @@ -620,9 +620,9 @@ table. == CreatePosts: migrated (0.0020s) =========================================== </shell> -NOTE. Because you're working in the development environment by default, this +NOTE. Because by default you're working in the development environment, this command will apply to the database defined in the +development+ section of your -+config/database.yml+ file. If you would like to execute migrations in other ++config/database.yml+ file. If you would like to execute migrations in another environment, for instance in production, you must explicitly pass it when invoking the command: <tt>rake db:migrate RAILS_ENV=production</tt>. @@ -704,8 +704,8 @@ $ rails console </shell> TIP: The default console will make changes to your database. You can instead -open a console that will roll back any changes you make by using +rails console ---sandbox+. +open a console that will roll back any changes you make by using <tt>rails console +--sandbox</tt>. After the console loads, you can use it to work with your application's models: @@ -783,7 +783,8 @@ Here's +app/views/posts/index.html.erb+: <td><%= post.content %></td> <td><%= link_to 'Show', post %></td> <td><%= link_to 'Edit', edit_post_path(post) %></td> - <td><%= link_to 'Destroy', post, :confirm => 'Are you sure?', :method => :delete %></td> + <td><%= link_to 'Destroy', post, :confirm => 'Are you sure?', + :method => :delete %></td> </tr> <% end %> </table> @@ -867,10 +868,10 @@ The +new.html.erb+ view displays this empty Post to the user: The +<%= render 'form' %>+ line is our first introduction to _partials_ in Rails. A partial is a snippet of HTML and Ruby code that can be reused in -multiple locations. In this case, the form used to make a new post, is basically -identical to a form used to edit a post, both have text fields for the name and -title and a text area for the content with a button to make a new post or update -the existing post. +multiple locations. In this case, the form used to make a new post is basically +identical to the form used to edit a post, both having text fields for the name and +title, a text area for the content, and a button to create the new post or to update +the existing one. If you take a look at +views/posts/_form.html.erb+ file, you will see the following: @@ -879,7 +880,8 @@ following: <%= form_for(@post) do |f| %> <% if @post.errors.any? %> <div id="errorExplanation"> - <h2><%= pluralize(@post.errors.count, "error") %> prohibited this post from being saved:</h2> + <h2><%= pluralize(@post.errors.count, "error") %> prohibited + this post from being saved:</h2> <ul> <% @post.errors.full_messages.each do |msg| %> <li><%= msg %></li> @@ -907,15 +909,15 @@ following: </erb> This partial receives all the instance variables defined in the calling view -file, so in this case, the controller assigned the new Post object to +@post+ -and so, this is available in both the view and partial as +@post+. +file. In this case, the controller assigned the new +Post+ object to +@post+, +which will thus be available in both the view and the partial as +@post+. For more information on partials, refer to the "Layouts and Rendering in Rails":layouts_and_rendering.html#using-partials guide. The +form_for+ block is used to create an HTML form. Within this block, you have access to methods to build various controls on the form. For example, -+f.text_field :name+ tells Rails to create a text input on the form, and to hook ++f.text_field :name+ tells Rails to create a text input on the form and to hook it up to the +name+ attribute of the instance being displayed. You can only use these methods with attributes of the model that the form is based on (in this case +name+, +title+, and +content+). Rails uses +form_for+ in preference to @@ -931,9 +933,9 @@ to a model, you should use the +form_tag+ method, which provides shortcuts for building forms that are not necessarily tied to a model instance. When the user clicks the +Create Post+ button on this form, the browser will -send information back to the +create+ method of the controller (Rails knows to -call the +create+ method because the form is sent with an HTTP POST request; -that's one of the conventions that I mentioned earlier): +send information back to the +create+ action of the controller (Rails knows to +call the +create+ action because the form is sent with an HTTP POST request; +that's one of the conventions that were mentioned earlier): <ruby> def create @@ -965,12 +967,12 @@ If the post was not successfully saved, due to a validation error, then the controller returns the user back to the +new+ action with any error messages so that the user has the chance to fix the error and try again. -The "Post was successfully created." message is stored inside of the Rails -+flash+ hash, (usually just called _the flash_) so that messages can be carried +The "Post was successfully created." message is stored in the Rails ++flash+ hash (usually just called _the flash_), so that messages can be carried over to another action, providing the user with useful information on the status of their request. In the case of +create+, the user never actually sees any page -rendered during the Post creation process, because it immediately redirects to -the new Post as soon Rails saves the record. The Flash carries over a message to +rendered during the post creation process, because it immediately redirects to +the new +Post+ as soon as Rails saves the record. The Flash carries over a message to the next action, so that when the user is redirected back to the +show+ action, they are presented with a message saying "Post was successfully created." @@ -1043,9 +1045,9 @@ it: <%= link_to 'Back', posts_path %> </erb> -Again, as with the +new+ action, the +edit+ action is using the +form+ partial, -this time however, the form will do a PUT action to the PostsController and the -submit button will display "Update Post" +Again, as with the +new+ action, the +edit+ action is using the +form+ partial. +This time, however, the form will do a PUT action to the +PostsController+ and the +submit button will display "Update Post". Submitting the form created by this view will invoke the +update+ action within the controller: @@ -1070,9 +1072,9 @@ end In the +update+ action, Rails first uses the +:id+ parameter passed back from the edit view to locate the database record that's being edited. The -+update_attributes+ call then takes the rest of the parameters from the request -and applies them to this record. If all goes well, the user is redirected to the -post's +show+ view. If there are any problems, it's back to the +edit+ view to ++update_attributes+ call then takes the +post+ parameter (a hash) from the request +and applies it to this record. If all goes well, the user is redirected to the +post's +show+ action. If there are any problems, it redirects back to the +edit+ action to correct them. h4. Destroying a Post @@ -1094,8 +1096,8 @@ end The +destroy+ method of an Active Record model instance removes the corresponding record from the database. After that's done, there isn't any -record to display, so Rails redirects the user's browser to the index view for -the model. +record to display, so Rails redirects the user's browser to the index action of +the controller. h3. Adding a Second Model @@ -1107,7 +1109,7 @@ h4. Generating a Model Models in Rails use a singular name, and their corresponding database tables use a plural name. For the model to hold comments, the convention is to use the name -Comment. Even if you don't want to use the entire apparatus set up by ++Comment+. Even if you don't want to use the entire apparatus set up by scaffolding, most Rails developers still use generators to make things like models and controllers. To create the new model, run this command in your terminal: @@ -1118,8 +1120,8 @@ $ rails generate model Comment commenter:string body:text post:references This command will generate four files: -* +app/models/comment.rb+ - The model -* +db/migrate/20100207235629_create_comments.rb+ - The migration +* +app/models/comment.rb+ - The model. +* +db/migrate/20100207235629_create_comments.rb+ - The migration. * +test/unit/comment_test.rb+ and +test/fixtures/comments.yml+ - The test harness. First, take a look at +comment.rb+: @@ -1177,8 +1179,8 @@ Active Record associations let you easily declare the relationship between two models. In the case of comments and posts, you could write out the relationships this way: -* Each comment belongs to one post -* One post can have many comments +* Each comment belongs to one post. +* One post can have many comments. In fact, this is very close to the syntax that Rails uses to declare this association. You've already seen the line of code inside the Comment model that @@ -1204,7 +1206,7 @@ end These two declarations enable a good bit of automatic behavior. For example, if you have an instance variable +@post+ containing a post, you can retrieve all -the comments belonging to that post as the array +@post.comments+. +the comments belonging to that post as an array using +@post.comments+. TIP: For more information on Active Record associations, see the "Active Record Associations":association_basics.html guide. @@ -1213,9 +1215,9 @@ h4. Adding a Route for Comments As with the +home+ controller, we will need to add a route so that Rails knows where we would like to navigate to see +comments+. Open up the -+config/routes.rb+ file again, you will see an entry that was added -automatically for +posts+ near the top by the scaffold generator, +resources -:posts+, edit it as follows: ++config/routes.rb+ file again. Near the top, you will see the entry for +posts+ +that was added automatically by the scaffold generator: <tt>resources +:posts</tt>. Edit it as follows: <ruby> resources :posts do @@ -1241,19 +1243,19 @@ $ rails generate controller Comments This creates six files and one empty directory: -* +app/controllers/comments_controller.rb+ - The controller -* +app/helpers/comments_helper.rb+ - A view helper file -* +test/functional/comments_controller_test.rb+ - The functional tests for the controller -* +test/unit/helpers/comments_helper_test.rb+ - The unit tests for the helper -* +app/views/comments/+ - Views of the controller are stored here -* +app/assets/stylesheets/comment.css.scss+ - Cascading style sheet for the controller -* +app/assets/javascripts/comment.js.coffee+ - CoffeeScript for the controller +* +app/controllers/comments_controller.rb+ - The controller. +* +app/helpers/comments_helper.rb+ - A view helper file. +* +test/functional/comments_controller_test.rb+ - The functional tests for the controller. +* +test/unit/helpers/comments_helper_test.rb+ - The unit tests for the helper. +* +app/views/comments/+ - Views of the controller are stored here. +* +app/assets/stylesheets/comment.css.scss+ - Cascading style sheet for the controller. +* +app/assets/javascripts/comment.js.coffee+ - CoffeeScript for the controller. Like with any blog, our readers will create their comments directly after reading the post, and once they have added their comment, will be sent back to the post show page to see their comment now listed. Due to this, our +CommentsController+ is there to provide a method to create comments and delete -SPAM comments when they arrive. +spam comments when they arrive. So first, we'll wire up the Post show template (+/app/views/posts/show.html.erb+) to let us make a new comment: @@ -1295,8 +1297,8 @@ So first, we'll wire up the Post show template <%= link_to 'Back to Posts', posts_path %> | </erb> -This adds a form on the Post show page that creates a new comment, which will -call the +CommentsController+ +create+ action, so let's wire that up: +This adds a form on the +Post+ show page that creates a new comment by +calling the +CommentsController+ +create+ action. Let's wire that up: <ruby> class CommentsController < ApplicationController @@ -1309,9 +1311,9 @@ end </ruby> You'll see a bit more complexity here than you did in the controller for posts. -That's a side-effect of the nesting that you've set up; each request for a +That's a side-effect of the nesting that you've set up. Each request for a comment has to keep track of the post to which the comment is attached, thus the -initial find action to the Post model to get the post in question. +initial call to the +find+ method of the +Post+ model to get the post in question. In addition, the code takes advantage of some of the methods available for an association. We use the +create+ method on +@post.comments+ to create and save @@ -1381,9 +1383,9 @@ right places. h3. Refactoring -Now that we have Posts and Comments working, if we take a look at the -+app/views/posts/show.html.erb+ template, it's getting long and awkward. We can -use partials to clean this up. +Now that we have posts and comments working, take a look at the ++app/views/posts/show.html.erb+ template. It is getting long and awkward. We can +use partials to clean it up. h4. Rendering Partial Collections @@ -1403,7 +1405,7 @@ following into it: </p> </erb> -Then in the +app/views/posts/show.html.erb+ you can change it to look like the +Then you can change +app/views/posts/show.html.erb+ to look like the following: <erb> @@ -1456,8 +1458,8 @@ comment to a local variable named the same as the partial, in this case h4. Rendering a Partial Form -Let's also move that new comment section out to its own partial. Again, you -create a file +app/views/comments/_form.html.erb+ and in it you put: +Let us also move that new comment section out to its own partial. Again, you +create a file +app/views/comments/_form.html.erb+ containing: <erb> <%= form_for([@post, @post.comments.build]) do |f| %> @@ -1508,7 +1510,7 @@ Then you make the +app/views/posts/show.html.erb+ look like the following: </erb> The second render just defines the partial template we want to render, -<tt>comments/form</tt>, Rails is smart enough to spot the forward slash in that +<tt>comments/form</tt>. Rails is smart enough to spot the forward slash in that string and realize that you want to render the <tt>_form.html.erb</tt> file in the <tt>app/views/comments</tt> directory. @@ -1517,7 +1519,7 @@ defined it as an instance variable. h3. Deleting Comments -Another important feature on a blog is being able to delete SPAM comments. To do +Another important feature of a blog is being able to delete spam comments. To do this, we need to implement a link of some sort in the view and a +DELETE+ action in the +CommentsController+. diff --git a/railties/guides/source/migrations.textile b/railties/guides/source/migrations.textile index 7faa18e888..9c92d567d3 100644 --- a/railties/guides/source/migrations.textile +++ b/railties/guides/source/migrations.textile @@ -91,13 +91,13 @@ Active Record provides methods that perform common data definition tasks in a da * +add_index+ * +remove_index+ -If you need to perform tasks specific to your database (for example create a "foreign key":#active-record-and-referential-integrity constraint) then the +execute+ function allows you to execute arbitrary SQL. A migration is just a regular Ruby class so you're not limited to these functions. For example after adding a column you could write code to set the value of that column for existing records (if necessary using your models). +If you need to perform tasks specific to your database (for example create a "foreign key":#active-record-and-referential-integrity constraint) then the +execute+ method allows you to execute arbitrary SQL. A migration is just a regular Ruby class so you're not limited to these functions. For example after adding a column you could write code to set the value of that column for existing records (if necessary using your models). On databases that support transactions with statements that change the schema (such as PostgreSQL or SQLite3), migrations are wrapped in a transaction. If the database does not support this (for example MySQL) then when a migration fails the parts of it that succeeded will not be rolled back. You will have to unpick the changes that were made by hand. h4. What's in a Name -Migrations are stored in files in +db/migrate+, one for each migration class. The name of the file is of the form +YYYYMMDDHHMMSS_create_products.rb+, that is to say a UTC timestamp identifying the migration followed by an underscore followed by the name of the migration. The name of the migration class (CamelCased version) should match the latter part of the file name. For example +20080906120000_create_products.rb+ should define +CreateProducts+ and +20080906120001_add_details_to_products.rb+ should define +AddDetailsToProducts+. If you do feel the need to change the file name then you <em>have to</em> update the name of the class inside or Rails will complain about a missing class. +Migrations are stored in files in +db/migrate+, one for each migration class. The name of the file is of the form +YYYYMMDDHHMMSS_create_products.rb+, that is to say a UTC timestamp identifying the migration followed by an underscore followed by the name of the migration. The name of the migration class (CamelCased version) should match the latter part of the file name. For example +20080906120000_create_products.rb+ should define class +CreateProducts+ and +20080906120001_add_details_to_products.rb+ should define +AddDetailsToProducts+. If you do feel the need to change the file name then you <em>have to</em> update the name of the class inside or Rails will complain about a missing class. Internally Rails only uses the migration's number (the timestamp) to identify them. Prior to Rails 2.1 the migration number started at 1 and was incremented each time a migration was generated. With multiple developers it was easy for these to clash requiring you to rollback migrations and renumber them. With Rails 2.1 this is largely avoided by using the creation time of the migration to identify them. You can revert to the old numbering scheme by adding the following line to +config/application.rb+. @@ -115,7 +115,7 @@ h4. Changing Migrations Occasionally you will make a mistake when writing a migration. If you have already run the migration then you cannot just edit the migration and run the migration again: Rails thinks it has already run the migration and so will do nothing when you run +rake db:migrate+. You must rollback the migration (for example with +rake db:rollback+), edit your migration and then run +rake db:migrate+ to run the corrected version. -In general editing existing migrations is not a good idea: you will be creating extra work for yourself and your co-workers and cause major headaches if the existing version of the migration has already been run on production machines. Instead you should write a new migration that performs the changes you require. Editing a freshly generated migration that has not yet been committed to source control (or more generally which has not been propagated beyond your development machine) is relatively harmless. +In general editing existing migrations is not a good idea: you will be creating extra work for yourself and your co-workers and cause major headaches if the existing version of the migration has already been run on production machines. Instead, you should write a new migration that performs the changes you require. Editing a freshly generated migration that has not yet been committed to source control (or, more generally, which has not been propagated beyond your development machine) is relatively harmless. h4. Supported Types @@ -134,7 +134,7 @@ Active Record supports the following types: * +:binary+ * +:boolean+ -These will be mapped onto an appropriate underlying database type, for example with MySQL +:string+ is mapped to +VARCHAR(255)+. You can create columns of types not supported by Active Record when using the non-sexy syntax, for example +These will be mapped onto an appropriate underlying database type. For example, with MySQL the type +:string+ is mapped to +VARCHAR(255)+. You can create columns of types not supported by Active Record when using the non-sexy syntax, for example <ruby> create_table :products do |t| @@ -148,7 +148,7 @@ h3. Creating a Migration h4. Creating a Model -The model and scaffold generators will create migrations appropriate for adding a new model. This migration will already contain instructions for creating the relevant table. If you tell Rails what columns you want then statements for adding those will also be created. For example, running +The model and scaffold generators will create migrations appropriate for adding a new model. This migration will already contain instructions for creating the relevant table. If you tell Rails what columns you want, then statements for adding these columns will also be created. For example, running <shell> $ rails generate model Product name:string description:text @@ -262,7 +262,7 @@ end which creates a +products+ table with a column called +name+ (and as discussed below, an implicit +id+ column). -The object yielded to the block allows you to create columns on the table. There are two ways of doing this: The first (traditional) form looks like +The object yielded to the block allows you to create columns on the table. There are two ways of doing it. The first (traditional) form looks like <ruby> create_table :products do |t| @@ -270,7 +270,7 @@ create_table :products do |t| end </ruby> -the second form, the so called "sexy" migration, drops the somewhat redundant +column+ method. Instead, the +string+, +integer+, etc. methods create a column of that type. Subsequent parameters are the same. +The second form, the so called "sexy" migration, drops the somewhat redundant +column+ method. Instead, the +string+, +integer+, etc. methods create a column of that type. Subsequent parameters are the same. <ruby> create_table :products do |t| @@ -278,7 +278,7 @@ create_table :products do |t| end </ruby> -By default +create_table+ will create a primary key called +id+. You can change the name of the primary key with the +:primary_key+ option (don't forget to update the corresponding model) or if you don't want a primary key at all (for example for a HABTM join table) you can pass +:id => false+. If you need to pass database specific options you can place an SQL fragment in the +:options+ option. For example +By default, +create_table+ will create a primary key called +id+. You can change the name of the primary key with the +:primary_key+ option (don't forget to update the corresponding model) or, if you don't want a primary key at all (for example for a HABTM join table), you can pass the option +:id => false+. If you need to pass database specific options you can place an SQL fragment in the +:options+ option. For example, <ruby> create_table :products, :options => "ENGINE=BLACKHOLE" do |t| @@ -286,7 +286,7 @@ create_table :products, :options => "ENGINE=BLACKHOLE" do |t| end </ruby> -will append +ENGINE=BLACKHOLE+ to the SQL statement used to create the table (when using MySQL the default is +ENGINE=InnoDB+). +will append +ENGINE=BLACKHOLE+ to the SQL statement used to create the table (when using MySQL, the default is +ENGINE=InnoDB+). h4. Changing Tables @@ -348,11 +348,11 @@ end </ruby> will add an +attachment_id+ column and a string +attachment_type+ column with a default value of 'Photo'. -NOTE: The +references+ helper does not actually create foreign key constraints for you. You will need to use +execute+ for that or a plugin that adds "foreign key support":#active-record-and-referential-integrity. +NOTE: The +references+ helper does not actually create foreign key constraints for you. You will need to use +execute+ or a plugin that adds "foreign key support":#active-record-and-referential-integrity. -If the helpers provided by Active Record aren't enough you can use the +execute+ function to execute arbitrary SQL. +If the helpers provided by Active Record aren't enough you can use the +execute+ method to execute arbitrary SQL. -For more details and examples of individual methods check the API documentation, in particular the documentation for "<tt>ActiveRecord::ConnectionAdapters::SchemaStatements</tt>":http://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/SchemaStatements.html (which provides the methods available in the +up+ and +down+ methods), "<tt>ActiveRecord::ConnectionAdapters::TableDefinition</tt>":http://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/TableDefinition.html (which provides the methods available on the object yielded by +create_table+) and "<tt>ActiveRecord::ConnectionAdapters::Table</tt>":http://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/Table.html (which provides the methods available on the object yielded by +change_table+). +For more details and examples of individual methods, check the API documentation, in particular the documentation for "<tt>ActiveRecord::ConnectionAdapters::SchemaStatements</tt>":http://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/SchemaStatements.html (which provides the methods available in the +up+ and +down+ methods), "<tt>ActiveRecord::ConnectionAdapters::TableDefinition</tt>":http://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/TableDefinition.html (which provides the methods available on the object yielded by +create_table+) and "<tt>ActiveRecord::ConnectionAdapters::Table</tt>":http://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/Table.html (which provides the methods available on the object yielded by +change_table+). h4. Writing Your +change+ Method @@ -371,7 +371,7 @@ If you're going to use other methods, you'll have to write the +up+ and +down+ m h4. Writing Your +down+ Method -The +down+ method of your migration should revert the transformations done by the +up+ method. In other words the database schema should be unchanged if you do an +up+ followed by a +down+. For example if you create a table in the +up+ method you should drop it in the +down+ method. It is wise to do things in precisely the reverse order to in the +up+ method. For example +The +down+ method of your migration should revert the transformations done by the +up+ method. In other words, the database schema should be unchanged if you do an +up+ followed by a +down+. For example, if you create a table in the +up+ method, you should drop it in the +down+ method. It is wise to reverse the transformations in precisely the reverse order they were made in the +up+ method. For example, <ruby> class ExampleMigration < ActiveRecord::Migration @@ -402,22 +402,22 @@ class ExampleMigration < ActiveRecord::Migration end </ruby> -Sometimes your migration will do something which is just plain irreversible, for example it might destroy some data. In cases like those when you can't reverse the migration you can raise +ActiveRecord::IrreversibleMigration+ from your +down+ method. If someone tries to revert your migration an error message will be displayed saying that it can't be done. +Sometimes your migration will do something which is just plain irreversible; for example, it might destroy some data. In such cases, you can raise +ActiveRecord::IrreversibleMigration+ from your +down+ method. If someone tries to revert your migration, an error message will be displayed saying that it can't be done. h3. Running Migrations -Rails provides a set of rake tasks to work with migrations which boils down to running certain sets of migrations. The very first migration related rake task you use will probably be +db:migrate+. In its most basic form it just runs the +up+ method for all the migrations that have not yet been run. If there are no such migrations it exits. +Rails provides a set of rake tasks to work with migrations which boil down to running certain sets of migrations. The very first migration related rake task you will use will probably be +db:migrate+. In its most basic form it just runs the +up+ method for all the migrations that have not yet been run. If there are no such migrations, it exits. Note that running the +db:migrate+ also invokes the +db:schema:dump+ task, which will update your db/schema.rb file to match the structure of your database. If you specify a target version, Active Record will run the required migrations (up or down) until it has reached the specified version. The -version is the numerical prefix on the migration's filename. For example to migrate to version 20080906120000 run +version is the numerical prefix on the migration's filename. For example, to migrate to version 20080906120000 run <shell> $ rake db:migrate VERSION=20080906120000 </shell> -If this is greater than the current version (i.e. it is migrating upwards) this will run the +up+ method on all migrations up to and including 20080906120000, if migrating downwards this will run the +down+ method on all the migrations down to, but not including, 20080906120000. +If version 20080906120000 is greater than the current version (i.e., it is migrating upwards), this will run the +up+ method on all migrations up to and including 20080906120000. If migrating downwards, this will run the +down+ method on all the migrations down to, but not including, 20080906120000. h4. Rolling Back @@ -435,13 +435,13 @@ $ rake db:rollback STEP=3 will run the +down+ method from the last 3 migrations. -The +db:migrate:redo+ task is a shortcut for doing a rollback and then migrating back up again. As with the +db:rollback+ task you can use the +STEP+ parameter if you need to go more than one version back, for example +The +db:migrate:redo+ task is a shortcut for doing a rollback and then migrating back up again. As with the +db:rollback+ task, you can use the +STEP+ parameter if you need to go more than one version back, for example <shell> $ rake db:migrate:redo STEP=3 </shell> -Neither of these Rake tasks do anything you could not do with +db:migrate+, they are simply more convenient since you do not need to explicitly specify the version to migrate to. +Neither of these Rake tasks do anything you could not do with +db:migrate+. They are simply more convenient, since you do not need to explicitly specify the version to migrate to. Lastly, the +db:reset+ task will drop the database, recreate it and load the current schema into it. @@ -449,7 +449,7 @@ NOTE: This is not the same as running all the migrations - see the section on "s h4. Being Specific -If you need to run a specific migration up or down the +db:migrate:up+ and +db:migrate:down+ tasks will do that. Just specify the appropriate version and the corresponding migration will have its +up+ or +down+ method invoked, for example +If you need to run a specific migration up or down, the +db:migrate:up+ and +db:migrate:down+ tasks will do that. Just specify the appropriate version and the corresponding migration will have its +up+ or +down+ method invoked, for example, <shell> $ rake db:migrate:up VERSION=20080906120000 @@ -511,11 +511,11 @@ generates the following output 20080906170109 CreateProducts: migrated (10.0097s) </shell> -If you just want Active Record to shut up then running +rake db:migrate VERBOSE=false+ will suppress all output. +If you just want Active Record to shut up, then running +rake db:migrate VERBOSE=false+ will suppress all output. h3. Using Models in Your Migrations -When creating or updating data in a migration it is often tempting to use one of your models. After all they exist to provide easy access to the underlying data. This can be done, but some caution should be observed. +When creating or updating data in a migration it is often tempting to use one of your models. After all, they exist to provide easy access to the underlying data. This can be done, but some caution should be observed. For example, problems occur when the model uses database columns which are (1) not currently in the database and (2) will be created by this or a subsequent migration. @@ -524,7 +524,7 @@ Consider this example, where Alice and Bob are working on the same code base whi Bob goes on vacation. Alice creates a migration for the +products+ table which adds a new column and initializes it. -She also adds a validation to the Product model for the new column. +She also adds a validation to the +Product+ model for the new column. <ruby> # db/migrate/20100513121110_add_flag_to_product.rb @@ -545,7 +545,7 @@ class Product < ActiveRecord::Base end </ruby> -Alice adds a second migration which adds and initializes another column to the +products+ table and also adds a validation to the Product model for the new column. +Alice adds a second migration which adds and initializes another column to the +products+ table and also adds a validation to the +Product+ model for the new column. <ruby> # db/migrate/20100515121110_add_fuzz_to_product.rb @@ -573,7 +573,7 @@ Bob comes back from vacation and: # updates the source - which contains both migrations and the latests version of the Product model. # runs outstanding migrations with +rake db:migrate+, which includes the one that updates the +Product+ model. -The migration crashes because when the model attempts to save, it tries to validate the second added column, which is not in the database when the _first_ migration runs. +The migration crashes because when the model attempts to save, it tries to validate the second added column, which is not in the database when the _first_ migration runs: <plain> rake aborted! @@ -584,7 +584,7 @@ undefined method `fuzz' for #<Product:0x000001049b14a0> A fix for this is to create a local model within the migration. This keeps rails from running the validations, so that the migrations run to completion. -When using a faux model, it's a good idea to call +Product.reset_column_information+ to refresh the ActiveRecord cache for the Product model prior to updating data in the database. +When using a faux model, it's a good idea to call +Product.reset_column_information+ to refresh the +ActiveRecord+ cache for the +Product+ model prior to updating data in the database. If Alice had done this instead, there would have been no problem: @@ -654,13 +654,11 @@ ActiveRecord::Schema.define(:version => 20080906171750) do end </ruby> -In many ways this is exactly what it is. This file is created by inspecting the database and expressing its structure using +create_table+, +add_index+, and so on. Because this is database independent it could be loaded into any database that Active Record supports. This could be very useful if you were to distribute an application that is able to run against multiple databases. +In many ways this is exactly what it is. This file is created by inspecting the database and expressing its structure using +create_table+, +add_index+, and so on. Because this is database-independent, it could be loaded into any database that Active Record supports. This could be very useful if you were to distribute an application that is able to run against multiple databases. -There is however a trade-off: +db/schema.rb+ cannot express database specific items such as foreign key constraints, triggers or stored procedures. While in a migration you can execute custom SQL statements, the schema dumper cannot reconstitute those statements from the database. If you are using features like this then you should set the schema format to +:sql+. +There is however a trade-off: +db/schema.rb+ cannot express database specific items such as foreign key constraints, triggers, or stored procedures. While in a migration you can execute custom SQL statements, the schema dumper cannot reconstitute those statements from the database. If you are using features like this, then you should set the schema format to +:sql+. -Instead of using Active Record's schema dumper the database's structure will be dumped using a tool specific to that database (via the +db:structure:dump+ Rake task) into +db/#{Rails.env}_structure.sql+. For example for PostgreSQL the +pg_dump+ utility is used and for MySQL this file will contain the output of +SHOW CREATE TABLE+ for the various tables. Loading this schema is simply a question of executing the SQL statements contained inside. - -By definition this will be a perfect copy of the database's structure but this will usually prevent loading the schema into a database other than the one used to create it. +Instead of using Active Record's schema dumper, the database's structure will be dumped using a tool specific to the database (via the +db:structure:dump+ Rake task) into +db/#{Rails.env}_structure.sql+. For example, for the PostgreSQL RDBMS, the +pg_dump+ utility is used. For MySQL, this file will contain the output of +SHOW CREATE TABLE+ for the various tables. Loading these schemas is simply a question of executing the SQL statements they contain. By definition, this will create a perfect copy of the database's structure. Using the +:sql+ schema format will, however, prevent loading the schema into a RDBMS other than the one used to create it. h4. Schema Dumps and Source Control @@ -670,6 +668,6 @@ h3. Active Record and Referential Integrity The Active Record way claims that intelligence belongs in your models, not in the database. As such, features such as triggers or foreign key constraints, which push some of that intelligence back into the database, are not heavily used. -Validations such as +validates :foreign_key, :uniqueness => true+ are one way in which models can enforce data integrity. The +:dependent+ option on associations allows models to automatically destroy child objects when the parent is destroyed. Like anything which operates at the application level these cannot guarantee referential integrity and so some people augment them with foreign key constraints. +Validations such as +validates :foreign_key, :uniqueness => true+ are one way in which models can enforce data integrity. The +:dependent+ option on associations allows models to automatically destroy child objects when the parent is destroyed. Like anything which operates at the application level, these cannot guarantee referential integrity and so some people augment them with foreign key constraints. Although Active Record does not provide any tools for working directly with such features, the +execute+ method can be used to execute arbitrary SQL. There are also a number of plugins such as "foreign_key_migrations":https://github.com/harukizaemon/redhillonrails/tree/master/foreign_key_migrations/ which add foreign key support to Active Record (including support for dumping foreign keys in +db/schema.rb+). |