548 lines
18 KiB
Ruby
548 lines
18 KiB
Ruby
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module ActiveRecord
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# = Active Record Reflection
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module Reflection # :nodoc:
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extend ActiveSupport::Concern
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included do
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class_attribute :reflections
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self.reflections = {}
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end
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# Reflection enables to interrogate Active Record classes and objects
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# about their associations and aggregations. This information can,
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# for example, be used in a form builder that takes an Active Record object
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# and creates input fields for all of the attributes depending on their type
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# and displays the associations to other objects.
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#
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# MacroReflection class has info for AggregateReflection and AssociationReflection
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# classes.
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module ClassMethods
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def create_reflection(macro, name, scope, options, active_record)
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case macro
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when :has_many, :belongs_to, :has_one, :has_and_belongs_to_many
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klass = options[:through] ? ThroughReflection : AssociationReflection
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reflection = klass.new(macro, name, scope, options, active_record)
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when :composed_of
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reflection = AggregateReflection.new(macro, name, scope, options, active_record)
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end
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self.reflections = self.reflections.merge(name => reflection)
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reflection
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end
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# Returns an array of AggregateReflection objects for all the aggregations in the class.
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def reflect_on_all_aggregations
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reflections.values.grep(AggregateReflection)
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end
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# Returns the AggregateReflection object for the named +aggregation+ (use the symbol).
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#
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# Account.reflect_on_aggregation(:balance) # => the balance AggregateReflection
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#
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def reflect_on_aggregation(aggregation)
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reflection = reflections[aggregation]
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reflection if reflection.is_a?(AggregateReflection)
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end
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# Returns an array of AssociationReflection objects for all the
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# associations in the class. If you only want to reflect on a certain
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# association type, pass in the symbol (<tt>:has_many</tt>, <tt>:has_one</tt>,
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# <tt>:belongs_to</tt>) as the first parameter.
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#
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# Example:
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#
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# Account.reflect_on_all_associations # returns an array of all associations
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# Account.reflect_on_all_associations(:has_many) # returns an array of all has_many associations
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#
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def reflect_on_all_associations(macro = nil)
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association_reflections = reflections.values.grep(AssociationReflection)
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macro ? association_reflections.select { |reflection| reflection.macro == macro } : association_reflections
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end
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# Returns the AssociationReflection object for the +association+ (use the symbol).
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#
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# Account.reflect_on_association(:owner) # returns the owner AssociationReflection
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# Invoice.reflect_on_association(:line_items).macro # returns :has_many
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#
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def reflect_on_association(association)
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reflection = reflections[association]
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reflection if reflection.is_a?(AssociationReflection)
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end
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# Returns an array of AssociationReflection objects for all associations which have <tt>:autosave</tt> enabled.
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def reflect_on_all_autosave_associations
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reflections.values.select { |reflection| reflection.options[:autosave] }
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end
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end
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# Abstract base class for AggregateReflection and AssociationReflection. Objects of
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# AggregateReflection and AssociationReflection are returned by the Reflection::ClassMethods.
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class MacroReflection
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# Returns the name of the macro.
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#
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# <tt>composed_of :balance, :class_name => 'Money'</tt> returns <tt>:balance</tt>
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# <tt>has_many :clients</tt> returns <tt>:clients</tt>
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attr_reader :name
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# Returns the macro type.
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#
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# <tt>composed_of :balance, :class_name => 'Money'</tt> returns <tt>:composed_of</tt>
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# <tt>has_many :clients</tt> returns <tt>:has_many</tt>
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attr_reader :macro
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attr_reader :scope
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# Returns the hash of options used for the macro.
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#
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# <tt>composed_of :balance, :class_name => 'Money'</tt> returns <tt>{ :class_name => "Money" }</tt>
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# <tt>has_many :clients</tt> returns +{}+
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attr_reader :options
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attr_reader :active_record
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attr_reader :plural_name # :nodoc:
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def initialize(macro, name, scope, options, active_record)
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@macro = macro
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@name = name
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@scope = scope
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@options = options
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@active_record = active_record
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@plural_name = active_record.pluralize_table_names ?
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name.to_s.pluralize : name.to_s
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end
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# Returns the class for the macro.
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#
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# <tt>composed_of :balance, :class_name => 'Money'</tt> returns the Money class
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# <tt>has_many :clients</tt> returns the Client class
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def klass
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@klass ||= class_name.constantize
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end
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# Returns the class name for the macro.
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#
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# <tt>composed_of :balance, :class_name => 'Money'</tt> returns <tt>'Money'</tt>
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# <tt>has_many :clients</tt> returns <tt>'Client'</tt>
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def class_name
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@class_name ||= (options[:class_name] || derive_class_name).to_s
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end
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# Returns +true+ if +self+ and +other_aggregation+ have the same +name+ attribute, +active_record+ attribute,
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# and +other_aggregation+ has an options hash assigned to it.
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def ==(other_aggregation)
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super ||
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other_aggregation.kind_of?(self.class) &&
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name == other_aggregation.name &&
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other_aggregation.options &&
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active_record == other_aggregation.active_record
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end
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private
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def derive_class_name
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name.to_s.camelize
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end
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end
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# Holds all the meta-data about an aggregation as it was specified in the
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# Active Record class.
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class AggregateReflection < MacroReflection #:nodoc:
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def mapping
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mapping = options[:mapping] || [name, name]
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mapping.first.is_a?(Array) ? mapping : [mapping]
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end
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end
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# Holds all the meta-data about an association as it was specified in the
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# Active Record class.
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class AssociationReflection < MacroReflection #:nodoc:
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# Returns the target association's class.
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#
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# class Author < ActiveRecord::Base
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# has_many :books
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# end
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#
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# Author.reflect_on_association(:books).klass
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# # => Book
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#
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# <b>Note:</b> Do not call +klass.new+ or +klass.create+ to instantiate
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# a new association object. Use +build_association+ or +create_association+
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# instead. This allows plugins to hook into association object creation.
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def klass
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@klass ||= active_record.send(:compute_type, class_name)
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end
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def initialize(*args)
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super
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@collection = [:has_many, :has_and_belongs_to_many].include?(macro)
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end
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# Returns a new, unsaved instance of the associated class. +options+ will
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# be passed to the class's constructor.
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def build_association(*options, &block)
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klass.new(*options, &block)
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end
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def table_name
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@table_name ||= klass.table_name
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end
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def quoted_table_name
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@quoted_table_name ||= klass.quoted_table_name
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end
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def join_table
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@join_table ||= options[:join_table] || derive_join_table
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end
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def foreign_key
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@foreign_key ||= options[:foreign_key] || derive_foreign_key
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end
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def foreign_type
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@foreign_type ||= options[:foreign_type] || "#{name}_type"
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end
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def type
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@type ||= options[:as] && "#{options[:as]}_type"
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end
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def primary_key_column
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@primary_key_column ||= klass.columns.find { |c| c.name == klass.primary_key }
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end
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def association_foreign_key
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@association_foreign_key ||= options[:association_foreign_key] || class_name.foreign_key
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end
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# klass option is necessary to support loading polymorphic associations
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def association_primary_key(klass = nil)
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options[:primary_key] || primary_key(klass || self.klass)
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end
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def active_record_primary_key
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@active_record_primary_key ||= options[:primary_key] || primary_key(active_record)
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end
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def counter_cache_column
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if options[:counter_cache] == true
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"#{active_record.name.demodulize.underscore.pluralize}_count"
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elsif options[:counter_cache]
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options[:counter_cache].to_s
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end
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end
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def columns(tbl_name)
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@columns ||= klass.connection.columns(tbl_name)
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end
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def reset_column_information
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@columns = nil
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end
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def check_validity!
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check_validity_of_inverse!
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if has_and_belongs_to_many? && association_foreign_key == foreign_key
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raise HasAndBelongsToManyAssociationForeignKeyNeeded.new(self)
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end
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end
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def check_validity_of_inverse!
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unless options[:polymorphic]
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if has_inverse? && inverse_of.nil?
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raise InverseOfAssociationNotFoundError.new(self)
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end
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end
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end
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def through_reflection
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nil
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end
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def source_reflection
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nil
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end
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# A chain of reflections from this one back to the owner. For more see the explanation in
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# ThroughReflection.
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def chain
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[self]
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end
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def nested?
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false
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end
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# An array of arrays of scopes. Each item in the outside array corresponds to a reflection
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# in the #chain.
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def scope_chain
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scope ? [[scope]] : [[]]
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end
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alias :source_macro :macro
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def has_inverse?
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@options[:inverse_of]
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end
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def inverse_of
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if has_inverse?
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@inverse_of ||= klass.reflect_on_association(options[:inverse_of])
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end
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end
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def polymorphic_inverse_of(associated_class)
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if has_inverse?
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if inverse_relationship = associated_class.reflect_on_association(options[:inverse_of])
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inverse_relationship
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else
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raise InverseOfAssociationNotFoundError.new(self, associated_class)
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end
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end
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end
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# Returns whether or not this association reflection is for a collection
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# association. Returns +true+ if the +macro+ is either +has_many+ or
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# +has_and_belongs_to_many+, +false+ otherwise.
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def collection?
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@collection
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end
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# Returns whether or not the association should be validated as part of
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# the parent's validation.
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#
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# Unless you explicitly disable validation with
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# <tt>:validate => false</tt>, validation will take place when:
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#
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# * you explicitly enable validation; <tt>:validate => true</tt>
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# * you use autosave; <tt>:autosave => true</tt>
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# * the association is a +has_many+ association
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def validate?
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!options[:validate].nil? ? options[:validate] : (options[:autosave] == true || macro == :has_many)
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end
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# Returns +true+ if +self+ is a +belongs_to+ reflection.
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def belongs_to?
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macro == :belongs_to
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end
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def has_and_belongs_to_many?
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macro == :has_and_belongs_to_many
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end
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def association_class
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case macro
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when :belongs_to
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if options[:polymorphic]
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Associations::BelongsToPolymorphicAssociation
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else
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Associations::BelongsToAssociation
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end
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when :has_and_belongs_to_many
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Associations::HasAndBelongsToManyAssociation
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when :has_many
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if options[:through]
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Associations::HasManyThroughAssociation
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else
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Associations::HasManyAssociation
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end
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when :has_one
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if options[:through]
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Associations::HasOneThroughAssociation
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else
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Associations::HasOneAssociation
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end
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end
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end
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private
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def derive_class_name
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class_name = name.to_s.camelize
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class_name = class_name.singularize if collection?
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class_name
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end
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def derive_foreign_key
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if belongs_to?
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"#{name}_id"
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elsif options[:as]
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"#{options[:as]}_id"
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else
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active_record.name.foreign_key
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end
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end
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def derive_join_table
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[active_record.table_name, klass.table_name].sort.join("\0").gsub(/^(.*_)(.+)\0\1(.+)/, '\1\2_\3').gsub("\0", "_")
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end
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def primary_key(klass)
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klass.primary_key || raise(UnknownPrimaryKey.new(klass))
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end
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end
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# Holds all the meta-data about a :through association as it was specified
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# in the Active Record class.
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class ThroughReflection < AssociationReflection #:nodoc:
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delegate :foreign_key, :foreign_type, :association_foreign_key,
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:active_record_primary_key, :type, :to => :source_reflection
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# Gets the source of the through reflection. It checks both a singularized
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# and pluralized form for <tt>:belongs_to</tt> or <tt>:has_many</tt>.
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#
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# class Post < ActiveRecord::Base
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# has_many :taggings
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# has_many :tags, :through => :taggings
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# end
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#
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def source_reflection
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@source_reflection ||= source_reflection_names.collect { |name| through_reflection.klass.reflect_on_association(name) }.compact.first
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end
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# Returns the AssociationReflection object specified in the <tt>:through</tt> option
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# of a HasManyThrough or HasOneThrough association.
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#
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# class Post < ActiveRecord::Base
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# has_many :taggings
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# has_many :tags, :through => :taggings
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# end
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#
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# tags_reflection = Post.reflect_on_association(:tags)
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# taggings_reflection = tags_reflection.through_reflection
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#
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def through_reflection
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@through_reflection ||= active_record.reflect_on_association(options[:through])
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end
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# Returns an array of reflections which are involved in this association. Each item in the
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# array corresponds to a table which will be part of the query for this association.
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#
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# The chain is built by recursively calling #chain on the source reflection and the through
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# reflection. The base case for the recursion is a normal association, which just returns
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# [self] as its #chain.
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def chain
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@chain ||= begin
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chain = source_reflection.chain + through_reflection.chain
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chain[0] = self # Use self so we don't lose the information from :source_type
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chain
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end
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end
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# Consider the following example:
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#
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# class Person
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# has_many :articles
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# has_many :comment_tags, :through => :articles
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# end
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#
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# class Article
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# has_many :comments
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# has_many :comment_tags, :through => :comments, :source => :tags
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# end
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#
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# class Comment
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# has_many :tags
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# end
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#
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# There may be scopes on Person.comment_tags, Article.comment_tags and/or Comment.tags,
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# but only Comment.tags will be represented in the #chain. So this method creates an array
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# of scopes corresponding to the chain.
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def scope_chain
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@scope_chain ||= begin
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scope_chain = source_reflection.scope_chain.map(&:dup)
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# Add to it the scope from this reflection (if any)
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scope_chain.first << scope if scope
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through_scope_chain = through_reflection.scope_chain
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if options[:source_type]
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through_scope_chain.first <<
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through_reflection.klass.where(foreign_type => options[:source_type])
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end
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# Recursively fill out the rest of the array from the through reflection
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scope_chain + through_scope_chain
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end
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end
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# The macro used by the source association
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def source_macro
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source_reflection.source_macro
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end
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# A through association is nested if there would be more than one join table
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def nested?
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chain.length > 2 || through_reflection.macro == :has_and_belongs_to_many
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end
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# We want to use the klass from this reflection, rather than just delegate straight to
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# the source_reflection, because the source_reflection may be polymorphic. We still
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# need to respect the source_reflection's :primary_key option, though.
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def association_primary_key(klass = nil)
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# Get the "actual" source reflection if the immediate source reflection has a
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# source reflection itself
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source_reflection = self.source_reflection
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while source_reflection.source_reflection
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source_reflection = source_reflection.source_reflection
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end
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source_reflection.options[:primary_key] || primary_key(klass || self.klass)
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end
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# Gets an array of possible <tt>:through</tt> source reflection names:
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#
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# [:singularized, :pluralized]
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#
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def source_reflection_names
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@source_reflection_names ||= (options[:source] ? [options[:source]] : [name.to_s.singularize, name]).collect { |n| n.to_sym }
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end
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def source_options
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source_reflection.options
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end
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def through_options
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through_reflection.options
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end
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def check_validity!
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if through_reflection.nil?
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raise HasManyThroughAssociationNotFoundError.new(active_record.name, self)
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end
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if through_reflection.options[:polymorphic]
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raise HasManyThroughAssociationPolymorphicThroughError.new(active_record.name, self)
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end
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if source_reflection.nil?
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raise HasManyThroughSourceAssociationNotFoundError.new(self)
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end
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if options[:source_type] && source_reflection.options[:polymorphic].nil?
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raise HasManyThroughAssociationPointlessSourceTypeError.new(active_record.name, self, source_reflection)
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end
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if source_reflection.options[:polymorphic] && options[:source_type].nil?
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raise HasManyThroughAssociationPolymorphicSourceError.new(active_record.name, self, source_reflection)
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end
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if macro == :has_one && through_reflection.collection?
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raise HasOneThroughCantAssociateThroughCollection.new(active_record.name, self, through_reflection)
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end
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|
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check_validity_of_inverse!
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end
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private
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def derive_class_name
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|
# get the class_name of the belongs_to association of the through reflection
|
|
options[:source_type] || source_reflection.class_name
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|
end
|
|
end
|
|
end
|
|
end
|