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module ActiveRecord
module Associations
# Association proxies in Active Record are middlemen between the object that
# holds the association, known as the <tt>@owner</tt>, and the actual associated
# object, known as the <tt>@target</tt>. The kind of association any proxy is
# about is available in <tt>@reflection</tt>. That's an instance of the class
# ActiveRecord::Reflection::AssociationReflection.
#
# For example, given
#
# class Blog < ActiveRecord::Base
# has_many :posts
# end
#
# blog = Blog.first
#
# the association proxy in <tt>blog.posts</tt> has the object in +blog+ as
# <tt>@owner</tt>, the collection of its posts as <tt>@target</tt>, and
# the <tt>@reflection</tt> object represents a <tt>:has_many</tt> macro.
#
# This class has most of the basic instance methods removed, and delegates
# unknown methods to <tt>@target</tt> via <tt>method_missing</tt>. As a
# corner case, it even removes the +class+ method and that's why you get
#
# blog.posts.class # => Array
#
# though the object behind <tt>blog.posts</tt> is not an Array, but an
# ActiveRecord::Associations::HasManyAssociation.
#
# The <tt>@target</tt> object is not \loaded until needed. For example,
#
# blog.posts.count
#
# is computed directly through SQL and does not trigger by itself the
# instantiation of the actual post records.
class CollectionProxy < Relation
delegate :target, :load_target, :loaded?, :to => :@association
##
# :method: concat
# Add +records+ to this association. Returns +self+ so method calls may
# be chained. Since << flattens its argument list and inserts each record,
# +push+ and +concat+ behave identically.
#
# class Person < ActiveRecord::Base
# pets :has_many
# end
#
# person.pets << Person.new(name: 'Nemo')
# person.pets.concat(Person.new(name: 'Droopy'))
# person.pets.push(Person.new(name: 'Ren'))
#
# person.pets # => [#<Pet name: "Nemo">, #<Pet name: "Droopy">, #<Pet name: "Ren">]
##
# :method: replace
# Replace this collection with +other_array+. This will perform a diff
# and delete/add only records that have changed.
#
# class Person < ActiveRecord::Base
# has_many :pets
# end
#
# person.pets
# # => [#<Pet id: 1, name: "Wy", group: "cats", person_id: 1>]
#
# other_pets = [Pet.new(name: 'GorbyPuff', group: 'celebrities']
#
# person.pets.replace(other_pets)
#
# person.pets
# # => [#<Pet id: 2, name: "GorbyPuff", group: "celebrities", person_id: 1>]
#
# If the supplied array has an incorrect association type, it raises
# an ActiveRecord::AssociationTypeMismatch error:
#
# person.pets.replace(["doo", "ggie", "gaga"])
# # => ActiveRecord::AssociationTypeMismatch: Pet expected, got String
##
# :method: destroy_all
# Destroy all the records from this association.
#
# class Person < ActiveRecord::Base
# has_many :pets
# end
#
# person.pets.size # => 3
#
# person.pets.destroy_all
#
# person.pets.size # => 0
# person.pets # => []
##
# :method: empty?
# Returns true if the collection is empty.
# Equivalent to +size.zero?+.
#
# class Person < ActiveRecord::Base
# has_many :pets
# end
#
# person.pets.count # => 1
# person.pets.empty? # => false
#
# person.pets.delete_all
# person.pets.count # => 0
# person.pets.empty? # => true
##
# :method: any?
# Returns true if the collections is not empty.
# Equivalent to +!collection.empty?+.
#
# class Person < ActiveRecord::Base
# has_many :pets
# end
#
# person.pets.count # => 0
# person.pets.any? # => false
#
# person.pets << Pet.new(name: 'Snoop')
# person.pets.count # => 0
# person.pets.any? # => true
#
# Also, you can pass a block to define a criteria. The behaviour
# is the same, it returns true if the collection based on the
# criteria is not empty.
#
# person.pets
# # => [#<Pet name: "Snoop", group: "dogs">]
#
# person.pets.any? do |pet|
# pet.group == 'cats'
# end
# # => false
#
# person.pets.any? do |pet|
# pet.group == 'dogs'
# end
# # => true
##
# :method: many?
# Returns true if the collection has more than 1 record.
# Equivalent to +collection.size > 1+.
#
# class Person < ActiveRecord::Base
# has_many :pets
# end
#
# person.pets.count #=> 1
# person.pets.many? #=> false
#
# person.pets << Pet.new(name: 'Snoopy')
# person.pets.count #=> 2
# person.pets.many? #=> true
#
# Also, you can pass a block to define a criteria. The
# behaviour is the same, it returns true if the collection
# based on the criteria has more than 1 record.
#
# person.pets
# # => [
# # #<Pet name: "GorbyPuff", group: "cats">,
# # #<Pet name: "Wy", group: "cats">,
# # #<Pet name: "Snoop", group: "dogs">
# # ]
#
# person.pets.many? do |pet|
# pet.group == 'dogs'
# end
# # => false
#
# person.pets.many? do |pet|
# pet.group == 'cats'
# end
# # => true
delegate :select, :find, :first, :last,
:build, :create, :create!,
:concat, :replace, :delete_all, :destroy_all, :delete, :destroy, :uniq,
:sum, :count, :size, :length, :empty?,
:any?, :many?, :include?,
:to => :@association
def initialize(association)
@association = association
super association.klass, association.klass.arel_table
merge! association.scoped
end
alias_method :new, :build
def proxy_association
@association
end
# We don't want this object to be put on the scoping stack, because
# that could create an infinite loop where we call an @association
# method, which gets the current scope, which is this object, which
# delegates to @association, and so on.
def scoping
@association.scoped.scoping { yield }
end
def spawn
scoped
end
def scoped(options = nil)
association = @association
super.extending! do
define_method(:proxy_association) { association }
end
end
def ==(other)
load_target == other
end
def to_ary
load_target.dup
end
alias_method :to_a, :to_ary
def <<(*records)
proxy_association.concat(records) && self
end
alias_method :push, :<<
def clear
delete_all
self
end
def reload
proxy_association.reload
self
end
end
end
end
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