diff options
Diffstat (limited to 'activerecord/lib/active_record/associations.rb')
| -rw-r--r-- | activerecord/lib/active_record/associations.rb | 69 |
1 files changed, 45 insertions, 24 deletions
diff --git a/activerecord/lib/active_record/associations.rb b/activerecord/lib/active_record/associations.rb index 0952ea2829..68f8bbeb1c 100644 --- a/activerecord/lib/active_record/associations.rb +++ b/activerecord/lib/active_record/associations.rb @@ -1,4 +1,3 @@ -require 'active_support/core_ext/array/wrap' require 'active_support/core_ext/enumerable' require 'active_support/core_ext/module/delegation' require 'active_support/core_ext/object/blank' @@ -70,7 +69,7 @@ module ActiveRecord end end - class HasManyThroughNestedAssociationsAreReadonly < ActiveRecordError #:nodoc + class HasManyThroughNestedAssociationsAreReadonly < ActiveRecordError #:nodoc: def initialize(owner, reflection) super("Cannot modify association '#{owner.class.name}##{reflection.name}' because it goes through more than one other association.") end @@ -196,6 +195,26 @@ module ActiveRecord # * <tt>Project#categories.empty?, Project#categories.size, Project#categories, Project#categories<<(category1),</tt> # <tt>Project#categories.delete(category1)</tt> # + # === Overriding generated methods + # + # Association methods are generated in a module that is included into the model class, + # which allows you to easily override with your own methods and call the original + # generated method with +super+. For example: + # + # class Car < ActiveRecord::Base + # belongs_to :owner + # belongs_to :old_owner + # def owner=(new_owner) + # self.old_owner = self.owner + # super + # end + # end + # + # If your model class is <tt>Project</tt>, the module is + # named <tt>Project::GeneratedFeatureMethods</tt>. The GeneratedFeatureMethods module is + # included in the model class immediately after the (anonymous) generated attributes methods + # module, meaning an association will override the methods for an attribute with the same name. + # # === A word of warning # # Don't create associations that have the same name as instance methods of @@ -524,7 +543,7 @@ module ActiveRecord # end # # @group = Group.first - # @group.users.collect { |u| u.avatar }.flatten # select all avatars for all users in the group + # @group.users.collect { |u| u.avatar }.compact # select all avatars for all users in the group # @group.avatars # selects all avatars by going through the User join model. # # An important caveat with going through +has_one+ or +has_many+ associations on the @@ -1078,8 +1097,8 @@ module ActiveRecord # alongside this object by calling their +destroy+ method. If set to <tt>:delete_all</tt> all associated # objects are deleted *without* calling their +destroy+ method. If set to <tt>:nullify</tt> all associated # objects' foreign keys are set to +NULL+ *without* calling their +save+ callbacks. If set to - # <tt>:restrict</tt> this object raises an <tt>ActiveRecord::DeleteRestrictionError</tt> exception and - # cannot be deleted if it has any associated objects. + # <tt>:restrict</tt> an error will be added to the object, preventing its deletion, if any associated + # objects are present. # # If using with the <tt>:through</tt> option, the association on the join model must be # a +belongs_to+, and the records which get deleted are the join records, rather than @@ -1110,7 +1129,7 @@ module ActiveRecord # it would skip the first 4 rows. # [:select] # By default, this is <tt>*</tt> as in <tt>SELECT * FROM</tt>, but can be changed if - # you, for example, want to do a join but not include the joined columns. Do not forget + # you want to do a join but not include the joined columns, for example. Do not forget # to include the primary and foreign keys, otherwise it will raise an error. # [:as] # Specifies a polymorphic interface (See <tt>belongs_to</tt>). @@ -1165,7 +1184,7 @@ module ActiveRecord # has_many :subscribers, :through => :subscriptions, :source => :user # has_many :subscribers, :class_name => "Person", :finder_sql => Proc.new { # %Q{ - # SELECT DISTINCT people.* + # SELECT DISTINCT * # FROM people p, post_subscriptions ps # WHERE ps.post_id = #{id} AND ps.person_id = p.id # ORDER BY p.first_name @@ -1232,8 +1251,8 @@ module ActiveRecord # If set to <tt>:destroy</tt>, the associated object is destroyed when this object is. If set to # <tt>:delete</tt>, the associated object is deleted *without* calling its destroy method. # If set to <tt>:nullify</tt>, the associated object's foreign key is set to +NULL+. - # Also, association is assigned. If set to <tt>:restrict</tt> this object raises an - # <tt>ActiveRecord::DeleteRestrictionError</tt> exception and cannot be deleted if it has any associated object. + # If set to <tt>:restrict</tt>, an error will be added to the object, preventing its deletion, if an + # associated object is present. # [:foreign_key] # Specify the foreign key used for the association. By default this is guessed to be the name # of this class in lower-case and "_id" suffixed. So a Person class that makes a +has_one+ association @@ -1245,8 +1264,8 @@ module ActiveRecord # [:as] # Specifies a polymorphic interface (See <tt>belongs_to</tt>). # [:select] - # By default, this is <tt>*</tt> as in <tt>SELECT * FROM</tt>, but can be changed if, for example, - # you want to do a join but not include the joined columns. Do not forget to include the + # By default, this is <tt>*</tt> as in <tt>SELECT * FROM</tt>, but can be changed if + # you want to do a join but not include the joined columns, for example. Do not forget to include the # primary and foreign keys, otherwise it will raise an error. # [:through] # Specifies a Join Model through which to perform the query. Options for <tt>:class_name</tt>, @@ -1336,7 +1355,7 @@ module ActiveRecord # SQL fragment, such as <tt>authorized = 1</tt>. # [:select] # By default, this is <tt>*</tt> as in <tt>SELECT * FROM</tt>, but can be changed - # if, for example, you want to do a join but not include the joined columns. Do not + # if you want to do a join but not include the joined columns, for example. Do not # forget to include the primary and foreign keys, otherwise it will raise an error. # [:foreign_key] # Specify the foreign key used for the association. By default this is guessed to be the name @@ -1363,7 +1382,9 @@ module ActiveRecord # and +decrement_counter+. The counter cache is incremented when an object of this # 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). You can also specify a custom counter + # 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 + # 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>.) # Note: Specifying a counter cache will add it to that model's list of readonly attributes @@ -1411,7 +1432,7 @@ module ActiveRecord # Specifies a many-to-many relationship with another class. This associates two classes via an # intermediate join table. Unless the join table is explicitly specified as an option, it is # guessed using the lexical order of the class names. So a join between Developer and Project - # will give the default join table name of "developers_projects" because "D" outranks "P". + # will give the default join table name of "developers_projects" because "D" precedes "P" alphabetically. # Note that this precedence is calculated using the <tt><</tt> operator for String. This # means that if the strings are of different lengths, and the strings are equal when compared # up to the shortest length, then the longer string is considered of higher @@ -1424,18 +1445,18 @@ module ActiveRecord # join table with a migration such as this: # # class CreateDevelopersProjectsJoinTable < ActiveRecord::Migration - # def self.up + # def change # create_table :developers_projects, :id => false do |t| # t.integer :developer_id # t.integer :project_id # end # end - # - # def self.down - # drop_table :developers_projects - # end # end # + # It's also a good idea to add indexes to each of those columns to speed up the joins process. + # However, in MySQL it is advised to add a compound index for both of the columns as MySQL only + # uses one index per table during the lookup. + # # Adds the following methods for retrieval and query: # # [collection(force_reload = false)] @@ -1493,8 +1514,8 @@ module ActiveRecord # * <tt>Developer#projects.size</tt> # * <tt>Developer#projects.find(id)</tt> # * <tt>Developer#projects.exists?(...)</tt> - # * <tt>Developer#projects.build</tt> (similar to <tt>Project.new("project_id" => id)</tt>) - # * <tt>Developer#projects.create</tt> (similar to <tt>c = Project.new("project_id" => id); c.save; c</tt>) + # * <tt>Developer#projects.build</tt> (similar to <tt>Project.new("developer_id" => id)</tt>) + # * <tt>Developer#projects.create</tt> (similar to <tt>c = Project.new("developer_id" => id); c.save; c</tt>) # The declaration may include an options hash to specialize the behavior of the association. # # === Options @@ -1555,8 +1576,8 @@ module ActiveRecord # An integer determining the offset from where the rows should be fetched. So at 5, # it would skip the first 4 rows. # [:select] - # By default, this is <tt>*</tt> as in <tt>SELECT * FROM</tt>, but can be changed if, for example, - # you want to do a join but not include the joined columns. Do not forget to include the primary + # By default, this is <tt>*</tt> as in <tt>SELECT * FROM</tt>, but can be changed if + # you want to do a join but exclude the joined columns, for example. Do not forget to include the primary # and foreign keys, otherwise it will raise an error. # [:readonly] # If true, all the associated objects are readonly through the association. @@ -1575,7 +1596,7 @@ module ActiveRecord # has_and_belongs_to_many :categories, :join_table => "prods_cats" # has_and_belongs_to_many :categories, :readonly => true # has_and_belongs_to_many :active_projects, :join_table => 'developers_projects', :delete_sql => - # "DELETE FROM developers_projects WHERE active=1 AND developer_id = #{id} AND project_id = #{record.id}" + # proc { |record| "DELETE FROM developers_projects WHERE active=1 AND developer_id = #{id} AND project_id = #{record.id}" } def has_and_belongs_to_many(name, options = {}, &extension) Builder::HasAndBelongsToMany.build(self, name, options, &extension) end |