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module ActiveRecord
module Associations
# This is the root class of all association proxies:
#
# AssociationProxy
# BelongsToAssociation
# HasOneAssociation
# BelongsToPolymorphicAssociation
# AssociationCollection
# HasAndBelongsToManyAssociation
# HasManyAssociation
# HasManyThroughAssociation
# HasOneThroughAssociation
#
# 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.find(: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 AssociationProxy #:nodoc:
alias_method :proxy_respond_to?, :respond_to?
alias_method :proxy_extend, :extend
delegate :to_param, :to => :proxy_target
instance_methods.each { |m| undef_method m unless m =~ /(^__|^nil\?$|^send$|proxy_|^object_id$)/ }
def initialize(owner, reflection)
@owner, @reflection = owner, reflection
Array(reflection.options[:extend]).each { |ext| proxy_extend(ext) }
reset
end
# Returns the owner of the proxy.
def proxy_owner
@owner
end
# Returns the reflection object that represents the association handled
# by the proxy.
def proxy_reflection
@reflection
end
# Returns the \target of the proxy, same as +target+.
def proxy_target
@target
end
# Does the proxy or its \target respond to +symbol+?
def respond_to?(*args)
proxy_respond_to?(*args) || (load_target && @target.respond_to?(*args))
end
# Forwards <tt>===</tt> explicitly to the \target because the instance method
# removal above doesn't catch it. Loads the \target if needed.
def ===(other)
load_target
other === @target
end
# Returns the name of the table of the related class:
#
# post.comments.aliased_table_name # => "comments"
#
def aliased_table_name
@reflection.klass.table_name
end
# Returns the SQL string that corresponds to the <tt>:conditions</tt>
# option of the macro, if given, or +nil+ otherwise.
def conditions
@conditions ||= interpolate_sql(@reflection.sanitized_conditions) if @reflection.sanitized_conditions
end
alias :sql_conditions :conditions
# Resets the \loaded flag to +false+ and sets the \target to +nil+.
def reset
@loaded = false
@target = nil
end
# Reloads the \target and returns +self+ on success.
def reload
reset
load_target
self unless @target.nil?
end
# Has the \target been already \loaded?
def loaded?
@loaded
end
# Asserts the \target has been loaded setting the \loaded flag to +true+.
def loaded
@loaded = true
end
# Returns the target of this proxy, same as +proxy_target+.
def target
@target
end
# Sets the target of this proxy to <tt>\target</tt>, and the \loaded flag to +true+.
def target=(target)
@target = target
loaded
end
# Forwards the call to the target. Loads the \target if needed.
def inspect
load_target
@target.inspect
end
def send(method, *args)
if proxy_respond_to?(method)
super
else
load_target
@target.send(method, *args)
end
end
protected
# Does the association have a <tt>:dependent</tt> option?
def dependent?
@reflection.options[:dependent]
end
# Returns a string with the IDs of +records+ joined with a comma, quoted
# if needed. The result is ready to be inserted into a SQL IN clause.
#
# quoted_record_ids(records) # => "23,56,58,67"
#
def quoted_record_ids(records)
records.map { |record| record.quoted_id }.join(',')
end
def interpolate_sql(sql, record = nil)
@owner.send(:interpolate_sql, sql, record)
end
# Forwards the call to the reflection class.
def sanitize_sql(sql)
@reflection.klass.send(:sanitize_sql, sql)
end
# Assigns the ID of the owner to the corresponding foreign key in +record+.
# If the association is polymorphic the type of the owner is also set.
def set_belongs_to_association_for(record)
if @reflection.options[:as]
record["#{@reflection.options[:as]}_id"] = @owner.id unless @owner.new_record?
record["#{@reflection.options[:as]}_type"] = @owner.class.base_class.name.to_s
else
unless @owner.new_record?
primary_key = @reflection.options[:primary_key] || :id
record[@reflection.primary_key_name] = @owner.send(primary_key)
end
end
end
# Merges into +options+ the ones coming from the reflection.
def merge_options_from_reflection!(options)
options.reverse_merge!(
:group => @reflection.options[:group],
:having => @reflection.options[:having],
:limit => @reflection.options[:limit],
:offset => @reflection.options[:offset],
:joins => @reflection.options[:joins],
:include => @reflection.options[:include],
:select => @reflection.options[:select],
:readonly => @reflection.options[:readonly]
)
end
# Forwards +with_scope+ to the reflection.
def with_scope(*args, &block)
@reflection.klass.send :with_scope, *args, &block
end
private
# Forwards any missing method call to the \target.
def method_missing(method, *args)
if load_target
unless @target.respond_to?(method)
message = "undefined method `#{method.to_s}' for \"#{@target}\":#{@target.class.to_s}"
raise NoMethodError, message
end
if block_given?
@target.send(method, *args) { |*block_args| yield(*block_args) }
else
@target.send(method, *args)
end
end
end
# Loads the \target if needed and returns it.
#
# This method is abstract in the sense that it relies on +find_target+,
# which is expected to be provided by descendants.
#
# If the \target is already \loaded it is just returned. Thus, you can call
# +load_target+ unconditionally to get the \target.
#
# ActiveRecord::RecordNotFound is rescued within the method, and it is
# not reraised. The proxy is \reset and +nil+ is the return value.
def load_target
return nil unless defined?(@loaded)
if !loaded? and (!@owner.new_record? || foreign_key_present)
@target = find_target
end
@loaded = true
@target
rescue ActiveRecord::RecordNotFound
reset
end
# Can be overwritten by associations that might have the foreign key
# available for an association without having the object itself (and
# still being a new record). Currently, only +belongs_to+ presents
# this scenario (both vanilla and polymorphic).
def foreign_key_present
false
end
# Raises ActiveRecord::AssociationTypeMismatch unless +record+ is of
# the kind of the class of the associated objects. Meant to be used as
# a sanity check when you are about to assign an associated record.
def raise_on_type_mismatch(record)
unless record.is_a?(@reflection.klass) || record.is_a?(@reflection.class_name.constantize)
message = "#{@reflection.class_name}(##{@reflection.klass.object_id}) expected, got #{record.class}(##{record.class.object_id})"
raise ActiveRecord::AssociationTypeMismatch, message
end
end
# Array#flatten has problems with recursive arrays. Going one level
# deeper solves the majority of the problems.
def flatten_deeper(array)
array.collect { |element| (element.respond_to?(:flatten) && !element.is_a?(Hash)) ? element.flatten : element }.flatten
end
# Returns the ID of the owner, quoted if needed.
def owner_quoted_id
@owner.quoted_id
end
end
end
end
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