Class: ActiveRecord::Associations::CollectionAssociation

Inherits:
Association show all
Defined in:
activerecord/lib/active_record/associations/collection_association.rb

Overview

Active Record Association Collection

CollectionAssociation is an abstract class that provides common stuff to ease the implementation of association proxies that represent collections. See the class hierarchy in AssociationProxy.

CollectionAssociation:
  HasAndBelongsToManyAssociation => has_and_belongs_to_many
  HasManyAssociation => has_many
    HasManyThroughAssociation + ThroughAssociation => has_many :through

CollectionAssociation class provides common methods to the collections defined by has_and_belongs_to_many, has_many or has_many with :through association option.

You need to be careful with assumptions regarding the target: The proxy does not fetch records from the database until it needs them, but new ones created with build are added to the target. So, the target may be non-empty and still lack children waiting to be read from the database. If you look directly to the database you cannot assume that's the entire collection because new records may have been added to the target, etc.

If you need to work on all current children, new and existing records, load_target and the loaded flag are your friends.

Instance Attribute Summary

Attributes inherited from Association

#owner, #reflection, #target

Instance Method Summary collapse

Methods inherited from Association

#aliased_table_name, #association_scope, #initialize, #initialize_attributes, #interpolate, #klass, #loaded!, #loaded?, #marshal_dump, #marshal_load, #reload, #reset_scope, #set_inverse_instance, #stale_target?, #target_scope

Constructor Details

This class inherits a constructor from ActiveRecord::Associations::Association

Instance Method Details

#add_to_target(record) {|record| ... } ⇒ Object

Yields:

  • (record)

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# File 'activerecord/lib/active_record/associations/collection_association.rb', line 369

def add_to_target(record)
  callback(:before_add, record)
  yield(record) if block_given?

  if association_scope.distinct_value && index = @target.index(record)
    @target[index] = record
  else
    @target << record
  end

  callback(:after_add, record)
  set_inverse_instance(record)

  record
end

#any?Boolean

Returns true if the collections is not empty. Equivalent to !collection.empty?.


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# File 'activerecord/lib/active_record/associations/collection_association.rb', line 309

def any?
  if block_given?
    load_target.any? { |*block_args| yield(*block_args) }
  else
    !empty?
  end
end

#build(attributes = {}, &block) ⇒ Object


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# File 'activerecord/lib/active_record/associations/collection_association.rb', line 108

def build(attributes = {}, &block)
  if attributes.is_a?(Array)
    attributes.collect { |attr| build(attr, &block) }
  else
    add_to_target(build_record(attributes)) do |record|
      yield(record) if block_given?
    end
  end
end

#concat(*records) ⇒ Object

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.


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# File 'activerecord/lib/active_record/associations/collection_association.rb', line 129

def concat(*records)
  load_target if owner.new_record?

  if owner.new_record?
    concat_records(records)
  else
    transaction { concat_records(records) }
  end
end

#count(column_name = nil, count_options = {}) ⇒ Object

Count all records using SQL. Construct options and pass them with scope to the target class's count.


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# File 'activerecord/lib/active_record/associations/collection_association.rb', line 200

def count(column_name = nil, count_options = {})
  column_name, count_options = nil, column_name if column_name.is_a?(Hash)

  relation = scope
  if association_scope.distinct_value
    # This is needed because 'SELECT count(DISTINCT *)..' is not valid SQL.
    column_name ||= reflection.klass.primary_key
    relation = relation.distinct
  end

  value = relation.count(column_name)

  limit  = options[:limit]
  offset = options[:offset]

  if limit || offset
    [ [value - offset.to_i, 0].max, limit.to_i ].min
  else
    value
  end
end

#create(attributes = {}, &block) ⇒ Object


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# File 'activerecord/lib/active_record/associations/collection_association.rb', line 118

def create(attributes = {}, &block)
  create_record(attributes, &block)
end

#create!(attributes = {}, &block) ⇒ Object


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# File 'activerecord/lib/active_record/associations/collection_association.rb', line 122

def create!(attributes = {}, &block)
  create_record(attributes, true, &block)
end

#delete(*records) ⇒ Object

Removes records from this association calling before_remove and after_remove callbacks.

This method is abstract in the sense that delete_records has to be provided by descendants. Note this method does not imply the records are actually removed from the database, that depends precisely on delete_records. They are in any case removed from the collection.


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# File 'activerecord/lib/active_record/associations/collection_association.rb', line 229

def delete(*records)
  _options = records.extract_options!
  dependent = _options[:dependent] || options[:dependent]

  if records.first == :all
    if loaded? || dependent == :destroy
      delete_or_destroy(load_target, dependent)
    else
      delete_records(:all, dependent)
    end
  else
    records = find(records) if records.any? { |record| record.kind_of?(Fixnum) || record.kind_of?(String) }
    delete_or_destroy(records, dependent)
  end
end

#delete_all(dependent = nil) ⇒ Object

Removes all records from the association without calling callbacks on the associated records. It honors the `:dependent` option. However if the `:dependent` value is `:destroy` then in that case the default deletion strategy for the association is applied.

You can force a particular deletion strategy by passing a parameter.

Example:

@author.books.delete_all(:nullify) @author.books.delete_all(:delete_all)

See delete for more info.


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# File 'activerecord/lib/active_record/associations/collection_association.rb', line 167

def delete_all(dependent = nil)
  if dependent.present? && ![:nullify, :delete_all].include?(dependent)
    raise ArgumentError, "Valid values are :nullify or :delete_all"
  end

  dependent = if dependent.present?
                dependent
              elsif options[:dependent] == :destroy
                # since delete_all should not invoke callbacks so use the default deletion strategy
                # for :destroy
                reflection.is_a?(ActiveRecord::Reflection::ThroughReflection) ? :delete_all : :nullify
              else
                options[:dependent]
              end

  delete(:all, dependent: dependent).tap do
    reset
    loaded!
  end
end

#destroy(*records) ⇒ Object

Deletes the records and removes them from this association calling before_remove , after_remove , before_destroy and after_destroy callbacks.

Note that this method removes records from the database ignoring the :dependent option.


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# File 'activerecord/lib/active_record/associations/collection_association.rb', line 250

def destroy(*records)
  records = find(records) if records.any? { |record| record.kind_of?(Fixnum) || record.kind_of?(String) }
  delete_or_destroy(records, :destroy)
end

#destroy_allObject

Destroy all the records from this association.

See destroy for more info.


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# File 'activerecord/lib/active_record/associations/collection_association.rb', line 191

def destroy_all
  destroy(load_target).tap do
    reset
    loaded!
  end
end

#distinctObject Also known as: uniq


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# File 'activerecord/lib/active_record/associations/collection_association.rb', line 327

def distinct
  seen = {}
  load_target.find_all do |record|
    seen[record.id] = true unless seen.key?(record.id)
  end
end

#empty?Boolean

Returns true if the collection is empty.

If the collection has been loaded it is equivalent to collection.size.zero?. If the collection has not been loaded, it is equivalent to collection.exists?. If the collection has not already been loaded and you are going to fetch the records anyway it is better to check collection.length.zero?.


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# File 'activerecord/lib/active_record/associations/collection_association.rb', line 299

def empty?
  if loaded?
    size.zero?
  else
    @target.blank? && !scope.exists?
  end
end

#find(*args) ⇒ Object


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# File 'activerecord/lib/active_record/associations/collection_association.rb', line 78

def find(*args)
  if block_given?
    load_target.find(*args) { |*block_args| yield(*block_args) }
  else
    if options[:inverse_of] && loaded?
      args = args.flatten
      raise RecordNotFound, "Couldn't find #{scope.klass.name} without an ID" if args.blank?

      result = find_by_scan(*args)

      result_size = Array(result).size
      if !result || result_size != args.size
        scope.raise_record_not_found_exception!(args, result_size, args.size)
      else
        result
      end
    else
      scope.find(*args)
    end
  end
end

#first(*args) ⇒ Object


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# File 'activerecord/lib/active_record/associations/collection_association.rb', line 100

def first(*args)
  first_or_last(:first, *args)
end

#ids_readerObject

Implements the ids reader method, e.g. foo.item_ids for Foo.has_many :items


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# File 'activerecord/lib/active_record/associations/collection_association.rb', line 46

def ids_reader
  if loaded?
    load_target.map do |record|
      record.send(reflection.association_primary_key)
    end
  else
    column  = "#{reflection.quoted_table_name}.#{reflection.association_primary_key}"
    scope.pluck(column)
  end
end

#ids_writer(ids) ⇒ Object

Implements the ids writer method, e.g. foo.item_ids= for Foo.has_many :items


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# File 'activerecord/lib/active_record/associations/collection_association.rb', line 58

def ids_writer(ids)
  pk_column = reflection.primary_key_column
  ids = Array(ids).reject { |id| id.blank? }
  ids.map! { |i| pk_column.type_cast(i) }
  replace(klass.find(ids).index_by { |r| r.id }.values_at(*ids))
end

#include?(record) ⇒ Boolean


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# File 'activerecord/lib/active_record/associations/collection_association.rb', line 348

def include?(record)
  if record.is_a?(reflection.klass)
    if record.new_record?
      include_in_memory?(record)
    else
      loaded? ? target.include?(record) : scope.exists?(record)
    end
  else
    false
  end
end

#last(*args) ⇒ Object


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# File 'activerecord/lib/active_record/associations/collection_association.rb', line 104

def last(*args)
  first_or_last(:last, *args)
end

#lengthObject

Returns the size of the collection calling size on the target.

If the collection has been already loaded length and size are equivalent. If not and you are going to need the records anyway this method will take one less query. Otherwise size is more efficient.


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# File 'activerecord/lib/active_record/associations/collection_association.rb', line 287

def length
  load_target.size
end

#load_targetObject


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# File 'activerecord/lib/active_record/associations/collection_association.rb', line 360

def load_target
  if find_target?
    @target = merge_target_lists(find_target, target)
  end

  loaded!
  target
end

#many?Boolean

Returns true if the collection has more than 1 record. Equivalent to collection.size > 1.


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# File 'activerecord/lib/active_record/associations/collection_association.rb', line 319

def many?
  if block_given?
    load_target.many? { |*block_args| yield(*block_args) }
  else
    size > 1
  end
end

#null_scope?Boolean


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# File 'activerecord/lib/active_record/associations/collection_association.rb', line 391

def null_scope?
  owner.new_record? && !foreign_key_present?
end

#reader(force_reload = false) ⇒ Object

Implements the reader method, e.g. foo.items for Foo.has_many :items


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# File 'activerecord/lib/active_record/associations/collection_association.rb', line 30

def reader(force_reload = false)
  if force_reload
    klass.uncached { reload }
  elsif stale_target?
    reload
  end

  @proxy ||= CollectionProxy.create(klass, self)
end

#replace(other_array) ⇒ Object

Replace this collection with other_array. This will perform a diff and delete/add only records that have changed.


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# File 'activerecord/lib/active_record/associations/collection_association.rb', line 337

def replace(other_array)
  other_array.each { |val| raise_on_type_mismatch!(val) }
  original_target = load_target.dup

  if owner.new_record?
    replace_records(other_array, original_target)
  else
    transaction { replace_records(other_array, original_target) }
  end
end

#resetObject


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# File 'activerecord/lib/active_record/associations/collection_association.rb', line 65

def reset
  super
  @target = []
end

#scope(opts = {}) ⇒ Object


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# File 'activerecord/lib/active_record/associations/collection_association.rb', line 385

def scope(opts = {})
  scope = super()
  scope.none! if opts.fetch(:nullify, true) && null_scope?
  scope
end

#select(select = nil) ⇒ Object


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# File 'activerecord/lib/active_record/associations/collection_association.rb', line 70

def select(select = nil)
  if block_given?
    load_target.select.each { |e| yield e }
  else
    scope.select(select)
  end
end

#sizeObject

Returns the size of the collection by executing a SELECT COUNT(*) query if the collection hasn't been loaded, and calling collection.size if it has.

If the collection has been already loaded size and length are equivalent. If not and you are going to need the records anyway length will take one less query. Otherwise size is more efficient.

This method is abstract in the sense that it relies on count_records, which is a method descendants have to provide.


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# File 'activerecord/lib/active_record/associations/collection_association.rb', line 265

def size
  if !find_target? || loaded?
    if association_scope.distinct_value
      target.uniq.size
    else
      target.size
    end
  elsif !loaded? && !association_scope.group_values.empty?
    load_target.size
  elsif !loaded? && !association_scope.distinct_value && target.is_a?(Array)
    unsaved_records = target.select { |r| r.new_record? }
    unsaved_records.size + count_records
  else
    count_records
  end
end

#transaction(*args) ⇒ Object

Starts a transaction in the association class's database connection.

class Author < ActiveRecord::Base
  has_many :books
end

Author.first.books.transaction do
  # same effect as calling Book.transaction
end

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# File 'activerecord/lib/active_record/associations/collection_association.rb', line 148

def transaction(*args)
  reflection.klass.transaction(*args) do
    yield
  end
end

#writer(records) ⇒ Object

Implements the writer method, e.g. foo.items= for Foo.has_many :items


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# File 'activerecord/lib/active_record/associations/collection_association.rb', line 41

def writer(records)
  replace(records)
end