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Diffstat (limited to 'guides/source/association_basics.md')
| -rw-r--r-- | guides/source/association_basics.md | 84 |
1 files changed, 67 insertions, 17 deletions
diff --git a/guides/source/association_basics.md b/guides/source/association_basics.md index 8d203d265a..9b80a65a44 100644 --- a/guides/source/association_basics.md +++ b/guides/source/association_basics.md @@ -693,6 +693,17 @@ There are a few limitations to `inverse_of` support: * They do not work with `:as` associations. * For `belongs_to` associations, `has_many` inverse associations are ignored. +Every association will attempt to automatically find the inverse association +and set the `:inverse_of` option heuristically (based on the association name). +Most associations with standard names will be supported. However, associations +that contain the following options will not have their inverses set +automatically: + +* :conditions +* :through +* :polymorphic +* :foreign_key + Detailed Association Reference ------------------------------ @@ -710,6 +721,7 @@ When you declare a `belongs_to` association, the declaring class automatically g * `association=(associate)` * `build_association(attributes = {})` * `create_association(attributes = {})` +* `create_association!(attributes = {})` In all of these methods, `association` is replaced with the symbol passed as the first argument to `belongs_to`. For example, given the declaration: @@ -726,6 +738,7 @@ customer customer= build_customer create_customer +create_customer! ``` NOTE: When initializing a new `has_one` or `belongs_to` association you must use the `build_` prefix to build the association, rather than the `association.build` method that would be used for `has_many` or `has_and_belongs_to_many` associations. To create one, use the `create_` prefix. @@ -766,6 +779,10 @@ The `create_association` method returns a new object of the associated type. Thi customer_name: "John Doe") ``` +##### `create_association!(attributes = {})` + +Does the same as `create_association` above, but raises `ActiveRecord::RecordInvalid` if the record is invalid. + #### Options for `belongs_to` @@ -936,7 +953,7 @@ end ##### `includes` -You can use the `includes` method let you specify second-order associations that should be eager-loaded when this association is used. For example, consider these models: +You can use the `includes` method to specify second-order associations that should be eager-loaded when this association is used. For example, consider these models: ```ruby class LineItem < ActiveRecord::Base @@ -1008,6 +1025,7 @@ When you declare a `has_one` association, the declaring class automatically gain * `association=(associate)` * `build_association(attributes = {})` * `create_association(attributes = {})` +* `create_association!(attributes = {})` In all of these methods, `association` is replaced with the symbol passed as the first argument to `has_one`. For example, given the declaration: @@ -1024,6 +1042,7 @@ account account= build_account create_account +create_account! ``` NOTE: When initializing a new `has_one` or `belongs_to` association you must use the `build_` prefix to build the association, rather than the `association.build` method that would be used for `has_many` or `has_and_belongs_to_many` associations. To create one, use the `create_` prefix. @@ -1062,6 +1081,10 @@ The `create_association` method returns a new object of the associated type. Thi @account = @supplier.create_account(terms: "Net 30") ``` +##### `create_association!(attributes = {})` + +Does the same as `create_association` above, but raises `ActiveRecord::RecordInvalid` if the record is invalid. + #### Options for `has_one` While Rails uses intelligent defaults that will work well in most situations, there may be times when you want to customize the behavior of the `has_one` association reference. Such customizations can easily be accomplished by passing options when you create the association. For example, this association uses two such options: @@ -1274,6 +1297,7 @@ When you declare a `has_many` association, the declaring class automatically gai * `collection.exists?(...)` * `collection.build(attributes = {}, ...)` * `collection.create(attributes = {})` +* `collection.create!(attributes = {})` In all of these methods, `collection` is replaced with the symbol passed as the first argument to `has_many`, and `collection_singular` is replaced with the singularized version of that symbol. For example, given the declaration: @@ -1301,6 +1325,7 @@ orders.where(...) orders.exists?(...) orders.build(attributes = {}, ...) orders.create(attributes = {}) +orders.create!(attributes = {}) ``` ##### `collection(force_reload = false)` @@ -1416,6 +1441,10 @@ The `collection.create` method returns a new object of the associated type. This order_number: "A12345") ``` +##### `collection.create!(attributes = {})` + +Does the same as `collection.create` above, but raises `ActiveRecord::RecordInvalid` if the record is invalid. + #### Options for `has_many` While Rails uses intelligent defaults that will work well in most situations, there may be times when you want to customize the behavior of the `has_many` association reference. Such customizations can easily be accomplished by passing options when you create the association. For example, this association uses two such options: @@ -1500,6 +1529,20 @@ end By convention, Rails assumes that the column used to hold the primary key of the association is `id`. You can override this and explicitly specify the primary key with the `:primary_key` option. +Let's say that `users` table has `id` as the primary_key but it also has +`guid` column. And the requirement is that `todos` table should hold +`guid` column value and not `id` value. This can be achieved like this + +```ruby +class User < ActiveRecord::Base + has_many :todos, primary_key: :guid +end +``` + +Now if we execute `@user.todos.create` then `@todo` record will have +`user_id` value as the `guid` value of `@user`. + + ##### `:source` The `:source` option specifies the source association name for a `has_many :through` association. You only need to use this option if the name of the source association cannot be automatically inferred from the association name. @@ -1667,7 +1710,7 @@ person.posts.inspect # => [#<Post id: 5, name: "a1">, #<Post id: 5, name: "a1">] Reading.all.inspect # => [#<Reading id: 12, person_id: 5, post_id: 5>, #<Reading id: 13, person_id: 5, post_id: 5>] ``` -In the above case there are two readings and `person.posts` brings out both of +In the above case there are two readings and `person.posts` brings out both of them even though these records are pointing to the same post. Now let's set `distinct`: @@ -1686,24 +1729,24 @@ person.posts.inspect # => [#<Post id: 7, name: "a1">] Reading.all.inspect # => [#<Reading id: 16, person_id: 7, post_id: 7>, #<Reading id: 17, person_id: 7, post_id: 7>] ``` -In the above case there are still two readings. However `person.posts` shows +In the above case there are still two readings. However `person.posts` shows only one post because the collection loads only unique records. -If you want to make sure that, upon insertion, all of the records in the -persisted association are distinct (so that you can be sure that when you -inspect the association that you will never find duplicate records), you should -add a unique index on the table itself. For example, if you have a table named -``person_posts`` and you want to make sure all the posts are unique, you could +If you want to make sure that, upon insertion, all of the records in the +persisted association are distinct (so that you can be sure that when you +inspect the association that you will never find duplicate records), you should +add a unique index on the table itself. For example, if you have a table named +`person_posts` and you want to make sure all the posts are unique, you could add the following in a migration: ```ruby -add_index :person_posts, :post, :unique => true +add_index :person_posts, :post, unique: true ``` -Note that checking for uniqueness using something like ``include?`` is subject -to race conditions. Do not attempt to use ``include?`` to enforce distinctness -in an association. For instance, using the post example from above, the -following code would be racy because multiple users could be attempting this +Note that checking for uniqueness using something like `include?` is subject +to race conditions. Do not attempt to use `include?` to enforce distinctness +in an association. For instance, using the post example from above, the +following code would be racy because multiple users could be attempting this at the same time: ```ruby @@ -1743,6 +1786,7 @@ When you declare a `has_and_belongs_to_many` association, the declaring class au * `collection.exists?(...)` * `collection.build(attributes = {})` * `collection.create(attributes = {})` +* `collection.create!(attributes = {})` In all of these methods, `collection` is replaced with the symbol passed as the first argument to `has_and_belongs_to_many`, and `collection_singular` is replaced with the singularized version of that symbol. For example, given the declaration: @@ -1770,6 +1814,7 @@ assemblies.where(...) assemblies.exists?(...) assemblies.build(attributes = {}, ...) assemblies.create(attributes = {}) +assemblies.create!(attributes = {}) ``` ##### Additional Column Methods @@ -1889,14 +1934,18 @@ The `collection.create` method returns a new object of the associated type. This @assembly = @part.assemblies.create({assembly_name: "Transmission housing"}) ``` +##### `collection.create!(attributes = {})` + +Does the same as `collection.create`, but raises `ActiveRecord::RecordInvalid` if the record is invalid. + #### Options for `has_and_belongs_to_many` While Rails uses intelligent defaults that will work well in most situations, there may be times when you want to customize the behavior of the `has_and_belongs_to_many` association reference. Such customizations can easily be accomplished by passing options when you create the association. For example, this association uses two such options: ```ruby class Parts < ActiveRecord::Base - has_and_belongs_to_many :assemblies, uniq: true, - read_only: true + has_and_belongs_to_many :assemblies, autosave: true, + readonly: true end ``` @@ -1908,6 +1957,7 @@ The `has_and_belongs_to_many` association supports these options: * `:foreign_key` * `:join_table` * `:validate` +* `:readonly` ##### `:association_foreign_key` @@ -1917,7 +1967,7 @@ TIP: The `:foreign_key` and `:association_foreign_key` options are useful when s ```ruby class User < ActiveRecord::Base - has_and_belongs_to_many :friends, + has_and_belongs_to_many :friends, class_name: "User", foreign_key: "this_user_id", association_foreign_key: "other_user_id" @@ -2122,7 +2172,7 @@ You're not limited to the functionality that Rails automatically builds into ass class Customer < ActiveRecord::Base has_many :orders do def find_by_order_prefix(order_number) - find_by_region_id(order_number[0..2]) + find_by(region_id: order_number[0..2]) end end end |