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Diffstat (limited to 'guides/source/association_basics.md')
| -rw-r--r-- | guides/source/association_basics.md | 15 |
1 files changed, 11 insertions, 4 deletions
diff --git a/guides/source/association_basics.md b/guides/source/association_basics.md index e6a66f3fa1..c58dd2e90a 100644 --- a/guides/source/association_basics.md +++ b/guides/source/association_basics.md @@ -40,7 +40,7 @@ end @customer.destroy ``` -With Active Record associations, we can streamline these — and other — operations by declaratively telling Rails that there is a connection between the two models. Here's the revised code for setting up customers and orders: +With Active Record associations, we can streamline these - and other - operations by declaratively telling Rails that there is a connection between the two models. Here's the revised code for setting up customers and orders: ```ruby class Customer < ActiveRecord::Base @@ -69,7 +69,7 @@ To learn more about the different types of associations, read the next section o The Types of Associations ------------------------- -In Rails, an _association_ is a connection between two Active Record models. Associations are implemented using macro-style calls, so that you can declaratively add features to your models. For example, by declaring that one model `belongs_to` another, you instruct Rails to maintain Primary Key–Foreign Key information between instances of the two models, and you also get a number of utility methods added to your model. Rails supports six types of associations: +In Rails, an _association_ is a connection between two Active Record models. Associations are implemented using macro-style calls, so that you can declaratively add features to your models. For example, by declaring that one model `belongs_to` another, you instruct Rails to maintain Primary Key-Foreign Key information between instances of the two models, and you also get a number of utility methods added to your model. Rails supports six types of associations: * `belongs_to` * `has_one` @@ -1137,6 +1137,12 @@ Controls what happens to the associated object when its owner is destroyed: * `:restrict_with_exception` causes an exception to be raised if there is an associated record * `:restrict_with_error` causes an error to be added to the owner if there is an associated object +It's necessary not to set or leave `:nullify` option for those associations +that have `NOT NULL` database constraints. If you don't set `dependent` to +destroy such associations you won't be able to change the associated object +because initial associated object foreign key will be set to unallowed `NULL` +value. + ##### `:foreign_key` By convention, Rails assumes that the column used to hold the foreign key on the other model is the name of this model with the suffix `_id` added. The `:foreign_key` option lets you set the name of the foreign key directly: @@ -1944,8 +1950,8 @@ While Rails uses intelligent defaults that will work well in most situations, th ```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 ``` @@ -1957,6 +1963,7 @@ The `has_and_belongs_to_many` association supports these options: * `:foreign_key` * `:join_table` * `:validate` +* `:readonly` ##### `:association_foreign_key` |