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Diffstat (limited to 'guides/source/active_record_basics.md')
| -rw-r--r-- | guides/source/active_record_basics.md | 41 |
1 files changed, 22 insertions, 19 deletions
diff --git a/guides/source/active_record_basics.md b/guides/source/active_record_basics.md index a184f0753d..a5196e481e 100644 --- a/guides/source/active_record_basics.md +++ b/guides/source/active_record_basics.md @@ -1,3 +1,5 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON http://guides.rubyonrails.org.** + Active Record Basics ==================== @@ -31,7 +33,7 @@ Object Relational Mapping system. in his book _Patterns of Enterprise Application Architecture_. In Active Record, objects carry both persistent data and behavior which operates on that data. Active Record takes the opinion that ensuring -data access logic is part of the object will educate users of that +data access logic as part of the object will educate users of that object on how to write to and read from the database. ### Object Relational Mapping @@ -60,7 +62,7 @@ Convention over Configuration in Active Record When writing applications using other programming languages or frameworks, it may be necessary to write a lot of configuration code. This is particularly true for ORM frameworks in general. However, if you follow the conventions adopted by -Rails, you'll need to write very little configuration (in some case no +Rails, you'll need to write very little configuration (in some cases no configuration at all) when creating Active Record models. The idea is that if you configure your applications in the very same way most of the time then this should be the default way. Thus, explicit configuration would be needed @@ -82,13 +84,13 @@ by underscores. Examples: * Model Class - Singular with the first letter of each word capitalized (e.g., `BookClub`). -| Model / Class | Table / Schema | -| ------------- | -------------- | -| `Post` | `posts` | -| `LineItem` | `line_items` | -| `Deer` | `deers` | -| `Mouse` | `mice` | -| `Person` | `people` | +| Model / Class | Table / Schema | +| ---------------- | -------------- | +| `Article` | `articles` | +| `LineItem` | `line_items` | +| `Deer` | `deers` | +| `Mouse` | `mice` | +| `Person` | `people` | ### Schema Conventions @@ -116,13 +118,13 @@ to Active Record instances: 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#label-Single+table+inheritance). + Inheritance](http://api.rubyonrails.org/classes/ActiveRecord/Base.html#class-ActiveRecord::Base-label-Single+table+inheritance). * `(association_name)_type` - Stores the type for [polymorphic associations](association_basics.html#polymorphic-associations). * `(table_name)_count` - Used to cache the number of belonging objects on - associations. For example, a `comments_count` column in a `Post` class that + associations. For example, a `comments_count` column in a `Articles` class that has many instances of `Comment` will cache the number of existent comments - for each post. + for each article. 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. @@ -309,11 +311,11 @@ into the database. There are several methods that you can use to check your models and validate that an attribute value is not empty, is unique and not already in the database, follows a specific format and many more. -Validation is a very important issue to consider when persisting to database, so -the methods `create`, `save` and `update` take it into account when +Validation is a very important issue to consider when persisting to the database, so +the methods `save` and `update` take it into account when running: they return `false` when validation fails and they didn't actually -perform any operation on database. All of these have a bang counterpart (that -is, `create!`, `save!` and `update!`), which are stricter in that +perform any operation on the database. All of these have a bang counterpart (that +is, `save!` and `update!`), which are stricter in that they raise the exception `ActiveRecord::RecordInvalid` if validation fails. A quick example to illustrate: @@ -322,8 +324,9 @@ class User < ActiveRecord::Base validates :name, presence: true end -User.create # => false -User.create! # => ActiveRecord::RecordInvalid: Validation failed: Name can't be blank +user = User.new +user.save # => false +user.save! # => ActiveRecord::RecordInvalid: Validation failed: Name can't be blank ``` You can learn more about validations in the [Active Record Validations @@ -357,7 +360,7 @@ class CreatePublications < ActiveRecord::Migration t.string :publisher_type t.boolean :single_issue - t.timestamps + t.timestamps null: false end add_index :publications, :publication_type_id end |