Class: ActiveRecord::Reflection::ThroughReflection

Inherits:
AbstractReflection show all
Defined in:
activerecord/lib/active_record/reflection.rb

Overview

Holds all the metadata about a :through association as it was specified in the Active Record class.

Instance Method Summary collapse

Methods inherited from AbstractReflection

#alias_candidate, #build_association, #build_scope, #chain, #check_validity_of_inverse!, #class_name, #counter_cache_column, #counter_must_be_updated_by_has_many?, #get_join_keys, #has_cached_counter?, #inverse_of, #inverse_updates_counter_in_memory?, #inverse_which_updates_counter_cache, #join_foreign_key, #join_keys, #join_primary_key, #join_scope, #klass_join_scope, #strict_loading?, #table_name

Constructor Details

#initialize(delegate_reflection) ⇒ ThroughReflection

Returns a new instance of ThroughReflection.


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# File 'activerecord/lib/active_record/reflection.rb', line 762

def initialize(delegate_reflection)
  @delegate_reflection = delegate_reflection
  @klass = delegate_reflection.options[:anonymous_class]
  @source_reflection_name = delegate_reflection.options[:source]
end

Instance Method Details

#add_as_polymorphic_through(reflection, seed) ⇒ Object


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# File 'activerecord/lib/active_record/reflection.rb', line 974

def add_as_polymorphic_through(reflection, seed)
  collect_join_reflections(seed + [PolymorphicReflection.new(self, reflection)])
end

#add_as_source(seed) ⇒ Object


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# File 'activerecord/lib/active_record/reflection.rb', line 970

def add_as_source(seed)
  collect_join_reflections seed
end

#add_as_through(seed) ⇒ Object


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# File 'activerecord/lib/active_record/reflection.rb', line 978

def add_as_through(seed)
  collect_join_reflections(seed + [self])
end

#association_primary_key(klass = nil) ⇒ Object

We want to use the klass from this reflection, rather than just delegate straight to the source_reflection, because the source_reflection may be polymorphic. We still need to respect the source_reflection's :primary_key option, though.


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# File 'activerecord/lib/active_record/reflection.rb', line 874

def association_primary_key(klass = nil)
  # Get the "actual" source reflection if the immediate source reflection has a
  # source reflection itself
  actual_source_reflection.options[:primary_key] || primary_key(klass || self.klass)
end

#check_validity!Object


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# File 'activerecord/lib/active_record/reflection.rb', line 924

def check_validity!
  if through_reflection.nil?
    raise HasManyThroughAssociationNotFoundError.new(active_record.name, self)
  end

  if through_reflection.polymorphic?
    if has_one?
      raise HasOneAssociationPolymorphicThroughError.new(active_record.name, self)
    else
      raise HasManyThroughAssociationPolymorphicThroughError.new(active_record.name, self)
    end
  end

  if source_reflection.nil?
    raise HasManyThroughSourceAssociationNotFoundError.new(self)
  end

  if options[:source_type] && !source_reflection.polymorphic?
    raise HasManyThroughAssociationPointlessSourceTypeError.new(active_record.name, self, source_reflection)
  end

  if source_reflection.polymorphic? && options[:source_type].nil?
    raise HasManyThroughAssociationPolymorphicSourceError.new(active_record.name, self, source_reflection)
  end

  if has_one? && through_reflection.collection?
    raise HasOneThroughCantAssociateThroughCollection.new(active_record.name, self, through_reflection)
  end

  if parent_reflection.nil?
    reflections = active_record.reflections.keys.map(&:to_sym)

    if reflections.index(through_reflection.name) > reflections.index(name)
      raise HasManyThroughOrderError.new(active_record.name, self, through_reflection)
    end
  end

  check_validity_of_inverse!
end

#clear_association_scope_cacheObject

This is for clearing cache on the reflection. Useful for tests that need to compare SQL queries on associations.


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# File 'activerecord/lib/active_record/reflection.rb', line 846

def clear_association_scope_cache # :nodoc:
  delegate_reflection.clear_association_scope_cache
  source_reflection.clear_association_scope_cache
  through_reflection.clear_association_scope_cache
end

#collect_join_chainObject

Returns an array of reflections which are involved in this association. Each item in the array corresponds to a table which will be part of the query for this association.

The chain is built by recursively calling #chain on the source reflection and the through reflection. The base case for the recursion is a normal association, which just returns

self

as its #chain.

class Post < ActiveRecord::Base
  has_many :taggings
  has_many :tags, through: :taggings
end

tags_reflection = Post.reflect_on_association(:tags)
tags_reflection.chain
# => [<ActiveRecord::Reflection::ThroughReflection: @delegate_reflection=#<ActiveRecord::Reflection::HasManyReflection: @name=:tags...>,
      <ActiveRecord::Reflection::HasManyReflection: @name=:taggings, @options={}, @active_record=Post>]

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# File 'activerecord/lib/active_record/reflection.rb', line 840

def collect_join_chain
  collect_join_reflections [self]
end

#constraintsObject


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# File 'activerecord/lib/active_record/reflection.rb', line 964

def constraints
  scope_chain = source_reflection.constraints
  scope_chain << scope if scope
  scope_chain
end

#has_scope?Boolean

Returns:

  • (Boolean)

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# File 'activerecord/lib/active_record/reflection.rb', line 860

def has_scope?
  scope || options[:source_type] ||
    source_reflection.has_scope? ||
    through_reflection.has_scope?
end

#join_scopes(table, predicate_builder) ⇒ Object

:nodoc:


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# File 'activerecord/lib/active_record/reflection.rb', line 856

def join_scopes(table, predicate_builder) # :nodoc:
  source_reflection.join_scopes(table, predicate_builder) + super
end

#klassObject


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# File 'activerecord/lib/active_record/reflection.rb', line 772

def klass
  @klass ||= delegate_reflection.compute_class(class_name).tap do |klass|
    if !parent_reflection.is_a?(HasAndBelongsToManyReflection) &&
       !(klass.reflections.key?(options[:through].to_s) ||
         klass.reflections.key?(options[:through].to_s.pluralize)) &&
       active_record.type_for_attribute(active_record.primary_key).type != :integer
      raise NotImplementedError, <<~MSG.squish
        In order to correctly type cast #{active_record}.#{active_record.primary_key},
        #{klass} needs to define a :#{options[:through]} association.
      MSG
    end
  end
end

#nested?Boolean

A through association is nested if there would be more than one join table

Returns:

  • (Boolean)

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# File 'activerecord/lib/active_record/reflection.rb', line 867

def nested?
  source_reflection.through_reflection? || through_reflection.through_reflection?
end

#scopesObject


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# File 'activerecord/lib/active_record/reflection.rb', line 852

def scopes
  source_reflection.scopes + super
end

#source_optionsObject


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# File 'activerecord/lib/active_record/reflection.rb', line 916

def source_options
  source_reflection.options
end

#source_reflectionObject

Returns the source of the through reflection. It checks both a singularized and pluralized form for :belongs_to or :has_many.

class Post < ActiveRecord::Base
  has_many :taggings
  has_many :tags, through: :taggings
end

class Tagging < ActiveRecord::Base
  belongs_to :post
  belongs_to :tag
end

tags_reflection = Post.reflect_on_association(:tags)
tags_reflection.source_reflection
# => <ActiveRecord::Reflection::BelongsToReflection: @name=:tag, @active_record=Tagging, @plural_name="tags">

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# File 'activerecord/lib/active_record/reflection.rb', line 803

def source_reflection
  through_reflection.klass._reflect_on_association(source_reflection_name)
end

#source_reflection_nameObject

:nodoc:


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# File 'activerecord/lib/active_record/reflection.rb', line 895

def source_reflection_name # :nodoc:
  return @source_reflection_name if @source_reflection_name

  names = [name.to_s.singularize, name].collect(&:to_sym).uniq
  names = names.find_all { |n|
    through_reflection.klass._reflect_on_association(n)
  }

  if names.length > 1
    raise AmbiguousSourceReflectionForThroughAssociation.new(
      active_record.name,
      macro,
      name,
      options,
      source_reflection_names
    )
  end

  @source_reflection_name = names.first
end

#source_reflection_namesObject

Gets an array of possible :through source reflection names in both singular and plural form.

class Post < ActiveRecord::Base
  has_many :taggings
  has_many :tags, through: :taggings
end

tags_reflection = Post.reflect_on_association(:tags)
tags_reflection.source_reflection_names
# => [:tag, :tags]

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# File 'activerecord/lib/active_record/reflection.rb', line 891

def source_reflection_names
  options[:source] ? [options[:source]] : [name.to_s.singularize, name].uniq
end

#through_optionsObject


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# File 'activerecord/lib/active_record/reflection.rb', line 920

def through_options
  through_reflection.options
end

#through_reflectionObject

Returns the AssociationReflection object specified in the :through option of a HasManyThrough or HasOneThrough association.

class Post < ActiveRecord::Base
  has_many :taggings
  has_many :tags, through: :taggings
end

tags_reflection = Post.reflect_on_association(:tags)
tags_reflection.through_reflection
# => <ActiveRecord::Reflection::HasManyReflection: @name=:taggings, @active_record=Post, @plural_name="taggings">

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# File 'activerecord/lib/active_record/reflection.rb', line 819

def through_reflection
  active_record._reflect_on_association(options[:through])
end

#through_reflection?Boolean

Returns:

  • (Boolean)

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# File 'activerecord/lib/active_record/reflection.rb', line 768

def through_reflection?
  true
end