diff options
Diffstat (limited to 'activerecord/lib/active_record/associations.rb')
| -rw-r--r-- | activerecord/lib/active_record/associations.rb | 63 |
1 files changed, 42 insertions, 21 deletions
diff --git a/activerecord/lib/active_record/associations.rb b/activerecord/lib/active_record/associations.rb index 5e5995f566..3490057298 100644 --- a/activerecord/lib/active_record/associations.rb +++ b/activerecord/lib/active_record/associations.rb @@ -172,7 +172,7 @@ module ActiveRecord @association_cache[name] = association end - # Associations are a set of macro-like class methods for tying objects together through + # \Associations are a set of macro-like class methods for tying objects together through # foreign keys. They express relationships like "Project has one Project Manager" # or "Project belongs to a Portfolio". Each macro adds a number of methods to the # class which are specialized according to the collection or association symbol and the @@ -365,11 +365,11 @@ module ActiveRecord # there is some special behavior you should be aware of, mostly involving the saving of # associated objects. # - # You can set the :autosave option on a <tt>has_one</tt>, <tt>belongs_to</tt>, + # You can set the <tt>:autosave</tt> option on a <tt>has_one</tt>, <tt>belongs_to</tt>, # <tt>has_many</tt>, or <tt>has_and_belongs_to_many</tt> association. Setting it # to +true+ will _always_ save the members, whereas setting it to +false+ will - # _never_ save the members. More details about :autosave option is available at - # autosave_association.rb . + # _never_ save the members. More details about <tt>:autosave</tt> option is available at + # AutosaveAssociation. # # === One-to-one associations # @@ -402,7 +402,7 @@ module ActiveRecord # # == Customizing the query # - # Associations are built from <tt>Relation</tt>s, and you can use the <tt>Relation</tt> syntax + # \Associations are built from <tt>Relation</tt>s, and you can use the <tt>Relation</tt> syntax # to customize them. For example, to add a condition: # # class Blog < ActiveRecord::Base @@ -568,6 +568,8 @@ module ActiveRecord # @group.avatars << Avatar.new # this would work if User belonged_to Avatar rather than the other way around # @group.avatars.delete(@group.avatars.last) # so would this # + # == Setting Inverses + # # If you are using a +belongs_to+ on the join model, it is a good idea to set the # <tt>:inverse_of</tt> option on the +belongs_to+, which will mean that the following example # works correctly (where <tt>tags</tt> is a +has_many+ <tt>:through</tt> association): @@ -584,7 +586,26 @@ module ActiveRecord # belongs_to :tag, inverse_of: :taggings # end # - # == Nested Associations + # If you do not set the +:inverse_of+ record, the association will do its + # best to match itself up with the correct inverse. Automatic +:inverse_of+ + # detection only works on +has_many+, +has_one+, and +belongs_to+ associations. + # + # Extra options on the associations, as defined in the + # <tt>AssociationReflection::INVALID_AUTOMATIC_INVERSE_OPTIONS</tt> constant, will + # also prevent the association's inverse from being found automatically. + # + # The automatic guessing of the inverse association uses a heuristic based + # on the name of the class, so it may not work for all associations, + # especially the ones with non-standard names. + # + # You can turn off the automatic detection of inverse associations by setting + # the +:automatic_inverse_of+ option to +false+ like so: + # + # class Taggable < ActiveRecord::Base + # belongs_to :tag, automatic_inverse_of: false + # end + # + # == Nested \Associations # # You can actually specify *any* association with the <tt>:through</tt> option, including an # association which has a <tt>:through</tt> option itself. For example: @@ -627,7 +648,7 @@ module ActiveRecord # add a <tt>Commenter</tt> in the example above, there would be no way to tell how to set up the # intermediate <tt>Post</tt> and <tt>Comment</tt> objects. # - # == Polymorphic Associations + # == Polymorphic \Associations # # Polymorphic associations on models are not restricted on what types of models they # can be associated with. Rather, they specify an interface that a +has_many+ association @@ -789,7 +810,7 @@ module ActiveRecord # For example if all the addressables are either of class Person or Company then a total # of 3 queries will be executed. The list of addressable types to load is determined on # the back of the addresses loaded. This is not supported if Active Record has to fallback - # to the previous implementation of eager loading and will raise ActiveRecord::EagerLoadPolymorphicError. + # to the previous implementation of eager loading and will raise <tt>ActiveRecord::EagerLoadPolymorphicError</tt>. # The reason is that the parent model's type is a column value so its corresponding table # name cannot be put in the +FROM+/+JOIN+ clauses of that query. # @@ -1024,7 +1045,7 @@ module ActiveRecord # An empty array is returned if none are found. # [collection<<(object, ...)] # Adds one or more objects to the collection by setting their foreign keys to the collection's primary key. - # Note that this operation instantly fires update sql without waiting for the save or update call on the + # Note that this operation instantly fires update SQL without waiting for the save or update call on the # parent object, unless the parent object is a new record. # [collection.delete(object, ...)] # Removes one or more objects from the collection by setting their foreign keys to +NULL+. @@ -1060,10 +1081,10 @@ module ActiveRecord # [collection.size] # Returns the number of associated objects. # [collection.find(...)] - # Finds an associated object according to the same rules as ActiveRecord::Base.find. + # Finds an associated object according to the same rules as <tt>ActiveRecord::Base.find</tt>. # [collection.exists?(...)] # Checks whether an associated object with the given conditions exists. - # Uses the same rules as ActiveRecord::Base.exists?. + # Uses the same rules as <tt>ActiveRecord::Base.exists?</tt>. # [collection.build(attributes = {}, ...)] # Returns one or more new objects of the collection type that have been instantiated # with +attributes+ and linked to this object through a foreign key, but have not yet @@ -1082,7 +1103,7 @@ module ActiveRecord # # === Example # - # Example: A Firm class declares <tt>has_many :clients</tt>, which will add: + # A <tt>Firm</tt> class declares <tt>has_many :clients</tt>, which will add: # * <tt>Firm#clients</tt> (similar to <tt>Client.where(firm_id: id)</tt>) # * <tt>Firm#clients<<</tt> # * <tt>Firm#clients.delete</tt> @@ -1116,8 +1137,8 @@ module ActiveRecord # Controls what happens to the associated objects when # their owner is destroyed. Note that these are implemented as # callbacks, and Rails executes callbacks in order. Therefore, other - # similar callbacks may affect the :dependent behavior, and the - # :dependent behavior may affect other callbacks. + # similar callbacks may affect the <tt>:dependent</tt> behavior, and the + # <tt>:dependent</tt> behavior may affect other callbacks. # # * <tt>:destroy</tt> causes all the associated objects to also be destroyed. # * <tt>:delete_all</tt> causes all the associated objects to be deleted directly from the database (so callbacks will not be executed). @@ -1163,8 +1184,8 @@ module ActiveRecord # If true, always save the associated objects or destroy them if marked for destruction, # when saving the parent object. If false, never save or destroy the associated objects. # By default, only save associated objects that are new records. This option is implemented as a - # before_save callback. Because callbacks are run in the order they are defined, associated objects - # may need to be explicitly saved in any user-defined before_save callbacks. + # +before_save+ callback. Because callbacks are run in the order they are defined, associated objects + # may need to be explicitly saved in any user-defined +before_save+ callbacks. # # Note that <tt>accepts_nested_attributes_for</tt> sets <tt>:autosave</tt> to <tt>true</tt>. # [:inverse_of] @@ -1189,7 +1210,7 @@ module ActiveRecord # Specifies a one-to-one association with another class. This method should only be used # if the other class contains the foreign key. If the current class contains the foreign key, # then you should use +belongs_to+ instead. See also ActiveRecord::Associations::ClassMethods's overview - # on when to use has_one and when to use belongs_to. + # on when to use +has_one+ and when to use +belongs_to+. # # The following methods for retrieval and query of a single associated object will be added: # @@ -1357,7 +1378,7 @@ module ActiveRecord # class is created and decremented when it's destroyed. This requires that a column # named <tt>#{table_name}_count</tt> (such as +comments_count+ for a belonging Comment class) # is used on the associate class (such as a Post class) - that is the migration for - # <tt>#{table_name}_count</tt> is created on the associate class (such that Post.comments_count will + # <tt>#{table_name}_count</tt> is created on the associate class (such that <tt>Post.comments_count</tt> will # return the count cached, see note below). You can also specify a custom counter # cache column by providing a column name instead of a +true+/+false+ value to this # option (e.g., <tt>counter_cache: :my_custom_counter</tt>.) @@ -1439,7 +1460,7 @@ module ActiveRecord # [collection<<(object, ...)] # Adds one or more objects to the collection by creating associations in the join table # (<tt>collection.push</tt> and <tt>collection.concat</tt> are aliases to this method). - # Note that this operation instantly fires update sql without waiting for the save or update call on the + # Note that this operation instantly fires update SQL without waiting for the save or update call on the # parent object, unless the parent object is a new record. # [collection.delete(object, ...)] # Removes one or more objects from the collection by removing their associations from the join table. @@ -1462,10 +1483,10 @@ module ActiveRecord # [collection.find(id)] # Finds an associated object responding to the +id+ and that # meets the condition that it has to be associated with this object. - # Uses the same rules as ActiveRecord::Base.find. + # Uses the same rules as <tt>ActiveRecord::Base.find</tt>. # [collection.exists?(...)] # Checks whether an associated object with the given conditions exists. - # Uses the same rules as ActiveRecord::Base.exists?. + # Uses the same rules as <tt>ActiveRecord::Base.exists?</tt>. # [collection.build(attributes = {})] # Returns a new object of the collection type that has been instantiated # with +attributes+ and linked to this object through the join table, but has not yet been saved. |