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Diffstat (limited to 'guides/source/association_basics.md')
| -rw-r--r-- | guides/source/association_basics.md | 31 |
1 files changed, 27 insertions, 4 deletions
diff --git a/guides/source/association_basics.md b/guides/source/association_basics.md index 05dd0d2a04..1191f5edfe 100644 --- a/guides/source/association_basics.md +++ b/guides/source/association_basics.md @@ -622,6 +622,19 @@ end We pass `id: false` to `create_table` because that table does not represent a model. That's required for the association to work properly. If you observe any strange behavior in a `has_and_belongs_to_many` association like mangled model IDs, or exceptions about conflicting IDs, chances are you forgot that bit. +You can also use the method `create_join_table` + +```ruby +class CreateAssembliesPartsJoinTable < ActiveRecord::Migration + def change + create_join_table :assemblies, :parts do |t| + t.index :assembly_id + t.index :part_id + end + end +end +``` + ### Controlling Association Scope By default, associations look for objects only within the current module's scope. This can be important when you declare Active Record models within a module. For example: @@ -1519,20 +1532,30 @@ conditions exists in the collection. It uses the same syntax and options as ##### `collection.build(attributes = {}, ...)` -The `collection.build` method returns one or more new objects of the associated type. These objects will be instantiated from the passed attributes, and the link through their foreign key will be created, but the associated objects will _not_ yet be saved. +The `collection.build` method returns a single or array of new objects of the associated type. The object(s) will be instantiated from the passed attributes, and the link through their foreign key will be created, but the associated objects will _not_ yet be saved. ```ruby @order = @customer.orders.build(order_date: Time.now, order_number: "A12345") + +@orders = @customer.orders.build([ + { order_date: Time.now, order_number: "A12346" }, + { order_date: Time.now, order_number: "A12347" } +]) ``` ##### `collection.create(attributes = {})` -The `collection.create` method returns a new object of the associated type. This object will be instantiated from the passed attributes, the link through its foreign key will be created, and, once it passes all of the validations specified on the associated model, the associated object _will_ be saved. +The `collection.create` method returns a single or array of new objects of the associated type. The object(s) will be instantiated from the passed attributes, the link through its foreign key will be created, and, once it passes all of the validations specified on the associated model, the associated object _will_ be saved. ```ruby @order = @customer.orders.create(order_date: Time.now, order_number: "A12345") + +@orders = @customer.orders.create([ + { order_date: Time.now, order_number: "A12346" }, + { order_date: Time.now, order_number: "A12347" } +]) ``` ##### `collection.create!(attributes = {})` @@ -2344,13 +2367,13 @@ associations, public methods, etc. Creating a car will save it in the `vehicles` table with "Car" as the `type` field: ```ruby -Car.create color: 'Red', price: 10000 +Car.create(color: 'Red', price: 10000) ``` will generate the following SQL: ```sql -INSERT INTO "vehicles" ("type", "color", "price") VALUES ("Car", "Red", 10000) +INSERT INTO "vehicles" ("type", "color", "price") VALUES ('Car', 'Red', 10000) ``` Querying car records will just search for vehicles that are cars: |