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Diffstat (limited to 'guides/source/association_basics.md')
| -rw-r--r-- | guides/source/association_basics.md | 64 |
1 files changed, 51 insertions, 13 deletions
diff --git a/guides/source/association_basics.md b/guides/source/association_basics.md index 16a5241319..d7277b487f 100644 --- a/guides/source/association_basics.md +++ b/guides/source/association_basics.md @@ -721,6 +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: @@ -737,6 +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. @@ -777,6 +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 <tt>create_association</tt> above, but raises <tt>ActiveRecord::RecordInvalid</tt> if the record is invalid. + #### Options for `belongs_to` @@ -1019,6 +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: @@ -1035,6 +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. @@ -1073,6 +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 <tt>create_association</tt> above, but raises <tt>ActiveRecord::RecordInvalid</tt> 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: @@ -1285,6 +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: @@ -1312,6 +1325,7 @@ orders.where(...) orders.exists?(...) orders.build(attributes = {}, ...) orders.create(attributes = {}) +orders.create!(attributes = {}) ``` ##### `collection(force_reload = false)` @@ -1427,6 +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 <tt>collection.create</tt> above, but raises <tt>ActiveRecord::RecordInvalid</tt> 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: @@ -1511,6 +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. @@ -1678,7 +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`: @@ -1697,24 +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 ``` -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 @@ -1754,6 +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: @@ -1781,6 +1814,7 @@ assemblies.where(...) assemblies.exists?(...) assemblies.build(attributes = {}, ...) assemblies.create(attributes = {}) +assemblies.create!(attributes = {}) ``` ##### Additional Column Methods @@ -1900,6 +1934,10 @@ 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 <tt>collection.create</tt>, but raises <tt>ActiveRecord::RecordInvalid</tt> 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: @@ -1928,7 +1966,7 @@ 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" @@ -2161,4 +2199,4 @@ Extensions can refer to the internals of the association proxy using these three * `proxy_association.owner` returns the object that the association is a part of. * `proxy_association.reflection` returns the reflection object that describes the association. -* `proxy_association.target` returns the associated object for `belongs_to` or `has_one`, or the collection of associated objects for `has_many` or `has_and_belongs_to_many`. +* `proxy_association.target` returns the associated object for `belongs_to` or `has_one`, or the collection of associated objects for `has_many` or `has_and_belongs_to_many`.
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