Class: ActiveRecord::Associations::CollectionProxy

Inherits:
Relation show all
Defined in:
activerecord/lib/active_record/associations/collection_proxy.rb

Overview

Association proxies in Active Record are middlemen between the object that holds the association, known as the @owner, and the actual associated object, known as the @target. The kind of association any proxy is about is available in @reflection. 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 blog.posts has the object in blog as @owner, the collection of its posts as @target, and the @reflection object represents a :has_many macro.

This class delegates unknown methods to @target via method_missing.

The @target 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.

Constant Summary

Constants inherited from Relation

Relation::INVALID_METHODS_FOR_DELETE_ALL, Relation::MULTI_VALUE_METHODS, Relation::SINGLE_VALUE_METHODS, Relation::VALUE_METHODS

Constants included from FinderMethods

FinderMethods::ONE_AS_ONE

Constants included from QueryMethods

QueryMethods::VALID_UNSCOPING_VALUES

Constants included from Delegation

Delegation::BLACKLISTED_ARRAY_METHODS

Instance Attribute Summary

Attributes inherited from Relation

#klass, #loaded, #table

Instance Method Summary collapse

Methods inherited from Relation

#_update_record, #as_json, #blank?, #eager_loading?, #encode_with, #explain, #find_or_create_by, #find_or_create_by!, #find_or_initialize_by, #first_or_create, #first_or_create!, #first_or_initialize, #initialize_copy, #insert, #inspect, #joined_includes_values, #load, #pretty_print, #scope_for_create, #substitute_values, #to_sql, #uniq_value, #update, #update_all, #values, #where_values_hash

Methods included from FinderMethods

#exists?, #fifth!, #find_by, #find_by!, #first!, #forty_two!, #fourth!, #last!, #raise_record_not_found_exception!, #second!, #take!, #third!

Methods included from Calculations

#average, #calculate, #ids, #maximum, #minimum, #pluck, #sum

Methods included from SpawnMethods

#except, #merge, #merge!, #only

Methods included from QueryMethods

#_select!, #bind, #bind!, #check_cached_relation, #create_with, #create_with!, #create_with_value, #distinct!, #eager_load, #eager_load!, #extending, #extending!, #from, #from!, #group, #group!, #having, #having!, #includes, #includes!, #joins, #joins!, #limit, #limit!, #lock, #lock!, #none, #none!, #offset, #offset!, #order, #order!, #preload, #preload!, #readonly, #readonly!, #references, #references!, #reorder, #reorder!, #reverse_order, #reverse_order!, #rewhere, #unscope, #unscope!, #where, #where!

Methods included from ActiveSupport::Concern

#append_features, #class_methods, extended, #included

Methods included from Batches

#find_each, #find_in_batches

Methods included from Explain

#collecting_queries_for_explain, #exec_explain

Methods included from Delegation

#respond_to?

Constructor Details

#initialize(klass, association) ⇒ CollectionProxy

:nodoc:


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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 34

def initialize(klass, association) #:nodoc:
  @association = association
  super klass, klass.arel_table
  merge! association.scope(nullify: false)
end

Dynamic Method Handling

This class handles dynamic methods through the method_missing method in the class ActiveRecord::Delegation

Instance Method Details

#<<(*records) ⇒ Object Also known as: push, append

Adds one or more records to the collection by setting their foreign keys to the association's primary key. Returns self, so several appends may be chained together.

class Person < ActiveRecord::Base
  has_many :pets
end

person.pets.size # => 0
person.pets << Pet.new(name: 'Fancy-Fancy')
person.pets << [Pet.new(name: 'Spook'), Pet.new(name: 'Choo-Choo')]
person.pets.size # => 3

person.id # => 1
person.pets# => [
#      #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#      #<Pet id: 2, name: "Spook", person_id: 1>,
#      #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]


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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 969

def <<(*records)
  proxy_association.concat(records) && self
end

#==(other) ⇒ Object

Equivalent to Array#==. Returns true if the two arrays contain the same number of elements and if each element is equal to the corresponding element in the other array, otherwise returns false.

class Person < ActiveRecord::Base
  has_many :pets
end

person.pets# => [
#      #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#      #<Pet id: 2, name: "Spook", person_id: 1>
#    ]


other = person.pets.to_ary

person.pets == other# => true


other = [Pet.new(id: 1), Pet.new(id: 2)]

person.pets == other# => false


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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 907

def ==(other)
  load_target == other
end

#any?(&block) ⇒ Boolean

Returns true if the collection is not 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

You can also pass a block to define criteria. The behavior 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

Returns:

  • (Boolean)

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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 805

def any?(&block)
  @association.any?(&block)
end

#arelObject


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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 861

def arel
  scope.arel
end

#build(attributes = {}, &block) ⇒ Object Also known as: new

Returns a new object of the collection type that has been instantiated with attributes and linked to this object, but have not yet been saved. You can pass an array of attributes hashes, this will return an array with the new objects.

class Person
  has_many :pets
end

person.pets.build# => #<Pet id: nil, name: nil, person_id: 1>


person.pets.build(name: 'Fancy-Fancy')# => #<Pet id: nil, name: "Fancy-Fancy", person_id: 1>


person.pets.build([{name: 'Spook'}, {name: 'Choo-Choo'}, {name: 'Brain'}])# => [
#      #<Pet id: nil, name: "Spook", person_id: 1>,
#      #<Pet id: nil, name: "Choo-Choo", person_id: 1>,
#      #<Pet id: nil, name: "Brain", person_id: 1>
#    ]


person.pets.size  # => 5 # size of the collection
person.pets.count # => 0 # count from database

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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 258

def build(attributes = {}, &block)
  @association.build(attributes, &block)
end

#clearObject

Equivalent to delete_all. The difference is that returns self, instead of an array with the deleted objects, so methods can be chained. See delete_all for more information.


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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 982

def clear
  delete_all
  self
end

#concat(*records) ⇒ Object

Add one or more records to the collection by setting their foreign keys to the association's primary key. Since << flattens its argument list and inserts each record, push and concat behave identically. Returns self so method calls may be chained.

class Person < ActiveRecord::Base
  has_many :pets
end

person.pets.size # => 0
person.pets.concat(Pet.new(name: 'Fancy-Fancy'))
person.pets.concat(Pet.new(name: 'Spook'), Pet.new(name: 'Choo-Choo'))
person.pets.size # => 3

person.id # => 1
person.pets# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]


person.pets.concat([Pet.new(name: 'Brain'), Pet.new(name: 'Benny')])
person.pets.size # => 5

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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 333

def concat(*records)
  @association.concat(*records)
end

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

Count all records using SQL.

class Person < ActiveRecord::Base
  has_many :pets
end

person.pets.count # => 3
person.pets# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]


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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 696

def count(column_name = nil, options = {})
  # TODO: Remove options argument as soon we remove support to
  # activerecord-deprecated_finders.
  @association.count(column_name, options)
end

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

Returns a new object of the collection type that has been instantiated with attributes, linked to this object and that has already been saved (if it passes the validations).

class Person
  has_many :pets
end

person.pets.create(name: 'Fancy-Fancy')# => #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>


person.pets.create([{name: 'Spook'}, {name: 'Choo-Choo'}])# => [
#      #<Pet id: 2, name: "Spook", person_id: 1>,
#      #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]


person.pets.size  # => 3
person.pets.count # => 3

person.pets.find(1, 2, 3)# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]


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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 289

def create(attributes = {}, &block)
  @association.create(attributes, &block)
end

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

Like create, except that if the record is invalid, raises an exception.

class Person
  has_many :pets
end

class Pet
  validates :name, presence: true
end

person.pets.create!(name: nil)# => ActiveRecord::RecordInvalid: Validation failed: Name can't be blank


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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 305

def create!(attributes = {}, &block)
  @association.create!(attributes, &block)
end

#delete(*records) ⇒ Object

Deletes the records supplied from the collection according to the strategy specified by the :dependent option. If no :dependent option is given, then it will follow the default strategy. Returns an array with the deleted records.

For has_many :through associations, the default deletion strategy is :delete_all.

For has_many associations, the default deletion strategy is :nullify. This sets the foreign keys to NULL.

class Person < ActiveRecord::Base
  has_many :pets # dependent: :nullify option by default
end

person.pets.size # => 3
person.pets# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]


person.pets.delete(Pet.find(1))# => [#<Pet id: 1, name: "Fancy-Fancy", person_id: 1>]


person.pets.size # => 2
person.pets# => [
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]


Pet.find(1)# => #<Pet id: 1, name: "Fancy-Fancy", person_id: nil>

If it is set to :destroy all the records are removed by calling their destroy method. See destroy for more information.

class Person < ActiveRecord::Base
  has_many :pets, dependent: :destroy
end

person.pets.size # => 3
person.pets# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]


person.pets.delete(Pet.find(1), Pet.find(3))# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]


person.pets.size # => 1
person.pets# => [#<Pet id: 2, name: "Spook", person_id: 1>]


Pet.find(1, 3)# => ActiveRecord::RecordNotFound: Couldn't find all Pets with IDs (1, 3)

If it is set to :delete_all, all the records are deleted without calling their destroy method.

class Person < ActiveRecord::Base
  has_many :pets, dependent: :delete_all
end

person.pets.size # => 3
person.pets# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]


person.pets.delete(Pet.find(1))# => [#<Pet id: 1, name: "Fancy-Fancy", person_id: 1>]


person.pets.size # => 2
person.pets# => [
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]


Pet.find(1)# => ActiveRecord::RecordNotFound: Couldn't find Pet with id=1

You can pass Integer or String values, it finds the records responding to the id and executes delete on them.

class Person < ActiveRecord::Base
  has_many :pets
end

person.pets.size # => 3
person.pets# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]


person.pets.delete("1")# => [#<Pet id: 1, name: "Fancy-Fancy", person_id: 1>]


person.pets.delete(2, 3)# => [
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]


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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 588

def delete(*records)
  @association.delete(*records)
end

#delete_all(dependent = nil) ⇒ Object

Deletes all the records from the collection according to the strategy specified by the :dependent option. If no :dependent option is given, then it will follow the default strategy.

For has_many :through associations, the default deletion strategy is :delete_all.

For has_many associations, the default deletion strategy is :nullify. This sets the foreign keys to NULL.

class Person < ActiveRecord::Base
  has_many :pets # dependent: :nullify option by default
end

person.pets.size # => 3
person.pets# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]


person.pets.delete_all# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]


person.pets.size # => 0
person.pets      # => []

Pet.find(1, 2, 3)# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: nil>,
#       #<Pet id: 2, name: "Spook", person_id: nil>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: nil>
#    ]

Both has_many and has_many :through dependencies default to the :delete_all strategy if the :dependent option is set to :destroy. Records are not instantiated and callbacks will not be fired.

class Person < ActiveRecord::Base
  has_many :pets, dependent: :destroy
end

person.pets.size # => 3
person.pets# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]


person.pets.delete_all

Pet.find(1, 2, 3)# => ActiveRecord::RecordNotFound

If it is set to :delete_all, all the objects are deleted without calling their destroy method.

class Person < ActiveRecord::Base
  has_many :pets, dependent: :delete_all
end

person.pets.size # => 3
person.pets# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]


person.pets.delete_all

Pet.find(1, 2, 3)# => ActiveRecord::RecordNotFound


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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 442

def delete_all(dependent = nil)
  @association.delete_all(dependent)
end

#destroy(*records) ⇒ Object

Destroys the records supplied and removes them from the collection. This method will always remove record from the database ignoring the :dependent option. Returns an array with the removed records.

class Person < ActiveRecord::Base
  has_many :pets
end

person.pets.size # => 3
person.pets# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]


person.pets.destroy(Pet.find(1))# => [#<Pet id: 1, name: "Fancy-Fancy", person_id: 1>]


person.pets.size # => 2
person.pets# => [
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]


person.pets.destroy(Pet.find(2), Pet.find(3))# => [
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]


person.pets.size  # => 0
person.pets       # => []

Pet.find(1, 2, 3) # => ActiveRecord::RecordNotFound: Couldn't find all Pets with IDs (1, 2, 3)

You can pass Integer or String values, it finds the records responding to the id and then deletes them from the database.

person.pets.size # => 3
person.pets# => [
#       #<Pet id: 4, name: "Benny", person_id: 1>,
#       #<Pet id: 5, name: "Brain", person_id: 1>,
#       #<Pet id: 6, name: "Boss",  person_id: 1>
#    ]


person.pets.destroy("4")# => #<Pet id: 4, name: "Benny", person_id: 1>


person.pets.size # => 2
person.pets# => [
#       #<Pet id: 5, name: "Brain", person_id: 1>,
#       #<Pet id: 6, name: "Boss",  person_id: 1>
#    ]


person.pets.destroy(5, 6)# => [
#       #<Pet id: 5, name: "Brain", person_id: 1>,
#       #<Pet id: 6, name: "Boss",  person_id: 1>
#    ]


person.pets.size  # => 0
person.pets       # => []

Pet.find(4, 5, 6) # => ActiveRecord::RecordNotFound: Couldn't find all Pets with IDs (4, 5, 6)

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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 660

def destroy(*records)
  @association.destroy(*records)
end

#destroy_allObject

Deletes the records of the collection directly from the database ignoring the :dependent option. Records are instantiated and it invokes before_remove, after_remove , before_destroy and after_destroy callbacks.

class Person < ActiveRecord::Base
  has_many :pets
end

person.pets.size # => 3
person.pets# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]


person.pets.destroy_all

person.pets.size # => 0
person.pets      # => []

Pet.find(1) # => Couldn't find Pet with id=1

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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 469

def destroy_all
  @association.destroy_all
end

#distinctObject Also known as: uniq

Specifies whether the records should be unique or not.

class Person < ActiveRecord::Base
  has_many :pets
end

person.pets.select(:name)# => [
#      #<Pet name: "Fancy-Fancy">,
#      #<Pet name: "Fancy-Fancy">
#    ]


person.pets.select(:name).distinct# => [#<Pet name: "Fancy-Fancy">]


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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 678

def distinct
  @association.distinct
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?.

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

Returns:

  • (Boolean)

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

def empty?
  @association.empty?
end

#fifth(*args) ⇒ Object

Same as first except returns only the fifth record.


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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 190

def fifth(*args)
  @association.fifth(*args)
end

#find(*args, &block) ⇒ Object

Finds an object in the collection responding to the id. Uses the same rules as ActiveRecord::Base.find. Returns ActiveRecord::RecordNotFound error if the object cannot be found.

class Person < ActiveRecord::Base
  has_many :pets
end

person.pets# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]


person.pets.find(1) # => #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>
person.pets.find(4) # => ActiveRecord::RecordNotFound: Couldn't find Pet with id=4

person.pets.find(2) { |pet| pet.name.downcase! }# => #<Pet id: 2, name: "fancy-fancy", person_id: 1>


person.pets.find(2, 3)# => [
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]


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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 140

def find(*args, &block)
  @association.find(*args, &block)
end

#first(*args) ⇒ Object

Returns the first record, or the first n records, from the collection. If the collection is empty, the first form returns nil, and the second form returns an empty array.

class Person < ActiveRecord::Base
  has_many :pets
end

person.pets# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]


person.pets.first # => #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>

person.pets.first(2)# => [
#      #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#      #<Pet id: 2, name: "Spook", person_id: 1>
#    ]


another_person_without.pets          # => []
another_person_without.pets.first    # => nil
another_person_without.pets.first(3) # => []

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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 170

def first(*args)
  @association.first(*args)
end

#forty_two(*args) ⇒ Object

Same as first except returns only the forty second record. Also known as accessing “the reddit”.


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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 196

def forty_two(*args)
  @association.forty_two(*args)
end

#fourth(*args) ⇒ Object

Same as first except returns only the fourth record.


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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 185

def fourth(*args)
  @association.fourth(*args)
end

#include?(record) ⇒ Boolean

Returns true if the given record is present in the collection.

class Person < ActiveRecord::Base
  has_many :pets
end

person.pets # => [#<Pet id: 20, name: "Snoop">]

person.pets.include?(Pet.find(20)) # => true
person.pets.include?(Pet.find(21)) # => false

Returns:

  • (Boolean)

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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 857

def include?(record)
  !!@association.include?(record)
end

#last(*args) ⇒ Object

Returns the last record, or the last n records, from the collection. If the collection is empty, the first form returns nil, and the second form returns an empty array.

class Person < ActiveRecord::Base
  has_many :pets
end

person.pets# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]


person.pets.last # => #<Pet id: 3, name: "Choo-Choo", person_id: 1>

person.pets.last(2)# => [
#      #<Pet id: 2, name: "Spook", person_id: 1>,
#      #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]


another_person_without.pets         # => []
another_person_without.pets.last    # => nil
another_person_without.pets.last(3) # => []

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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 226

def last(*args)
  @association.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.

class Person < ActiveRecord::Base
  has_many :pets
end

person.pets.length # => 3
# executes something like SELECT "pets".* FROM "pets" WHERE "pets"."person_id" = 1

# Because the collection is loaded, you can
# call the collection with no additional queries:
person.pets# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]


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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 750

def length
  @association.length
end

#load_targetObject


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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 44

def load_target
  @association.load_target
end

#loaded?Boolean

Returns true if the association has been loaded, otherwise false.

person.pets.loaded? # => false
person.pets
person.pets.loaded? # => true

Returns:

  • (Boolean)

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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 53

def loaded?
  @association.loaded?
end

#many?(&block) ⇒ Boolean

Returns true if the collection has more than one 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

You can also pass a block to define criteria. The behavior is the same, it returns true if the collection based on the criteria has more than one record.

person.pets# => [
#      #<Pet name: "Gorby", group: "cats">,
#      #<Pet name: "Puff", 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

Returns:

  • (Boolean)

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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 843

def many?(&block)
  @association.many?(&block)
end

#prepend(*args) ⇒ Object

Raises:

  • (NoMethodError)

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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 975

def prepend(*args)
  raise NoMethodError, "prepend on association is not defined. Please use << or append"
end

#proxy_associationObject


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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 865

def proxy_association
  @association
end

#reloadObject

Reloads the collection from the database. Returns self. Equivalent to collection(true).

class Person < ActiveRecord::Base
  has_many :pets
end

person.pets # fetches pets from the database
# => [#<Pet id: 1, name: "Snoop", group: "dogs", person_id: 1>]

person.pets # uses the pets cache
# => [#<Pet id: 1, name: "Snoop", group: "dogs", person_id: 1>]

person.pets.reload # fetches pets from the database
# => [#<Pet id: 1, name: "Snoop", group: "dogs", person_id: 1>]

person.pets(true)  # fetches pets from the database
# => [#<Pet id: 1, name: "Snoop", group: "dogs", person_id: 1>]

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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 1005

def reload
  proxy_association.reload
  self
end

#replace(other_array) ⇒ Object

Replaces 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: "Gorby", group: "cats", person_id: 1>]

other_pets = [Pet.new(name: 'Puff', group: 'celebrities']

person.pets.replace(other_pets)

person.pets
# => [#<Pet id: 2, name: "Puff", 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


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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 359

def replace(other_array)
  @association.replace(other_array)
end

#resetObject

Unloads the association. Returns self.

class Person < ActiveRecord::Base
  has_many :pets
end

person.pets # fetches pets from the database
# => [#<Pet id: 1, name: "Snoop", group: "dogs", person_id: 1>]

person.pets # uses the pets cache
# => [#<Pet id: 1, name: "Snoop", group: "dogs", person_id: 1>]

person.pets.reset # clears the pets cache

person.pets  # fetches pets from the database
# => [#<Pet id: 1, name: "Snoop", group: "dogs", person_id: 1>]

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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 1026

def reset
  proxy_association.reset
  proxy_association.reset_scope
  self
end

#scopeObject Also known as: spawn

Returns a Relation object for the records in this association


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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 878

def scope
  @association.scope
end

#scopingObject

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.


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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 873

def scoping
  @association.scope.scoping { yield }
end

#second(*args) ⇒ Object

Same as first except returns only the second record.


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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 175

def second(*args)
  @association.second(*args)
end

#select(*fields, &block) ⇒ Object

Works in two ways.

First: Specify a subset of fields to be selected from the result set.

class Person < ActiveRecord::Base
  has_many :pets
end

person.pets# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]


person.pets.select(:name)# => [
#      #<Pet id: nil, name: "Fancy-Fancy">,
#      #<Pet id: nil, name: "Spook">,
#      #<Pet id: nil, name: "Choo-Choo">
#    ]


person.pets.select(:id, :name )# => [
#      #<Pet id: 1, name: "Fancy-Fancy">,
#      #<Pet id: 2, name: "Spook">,
#      #<Pet id: 3, name: "Choo-Choo">
#    ]

Be careful because this also means you're initializing a model object with only the fields that you've selected. If you attempt to access a field except id that is not in the initialized record you'll receive:

person.pets.select(:name).first.person_id# => ActiveModel::MissingAttributeError: missing attribute: person_id

Second: You can pass a block so it can be used just like Array#select. This builds an array of objects from the database for the scope, converting them into an array and iterating through them using Array#select.

person.pets.select { |pet| pet.name =~ /oo/ }# => [
#      #<Pet id: 2, name: "Spook", person_id: 1>,
#      #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]


person.pets.select(:name) { |pet| pet.name =~ /oo/ }# => [
#      #<Pet id: 2, name: "Spook">,
#      #<Pet id: 3, name: "Choo-Choo">
#    ]


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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 110

def select(*fields, &block)
  @association.select(*fields, &block)
end

#sizeObject

Returns the size of the collection. If the collection hasn't been loaded, it executes a SELECT COUNT(*) query. Else it calls collection.size.

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.

class Person < ActiveRecord::Base
  has_many :pets
end

person.pets.size # => 3
# executes something like SELECT COUNT(*) FROM "pets" WHERE "pets"."person_id" = 1

person.pets # This will execute a SELECT * FROM query
# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]

person.pets.size # => 3
# Because the collection is already loaded, this will behave like
# collection.size and no SQL count query is executed.

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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 726

def size
  @association.size
end

#take(n = nil) ⇒ Object


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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 230

def take(n = nil)
  @association.take(n)
end

#targetObject


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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 40

def target
  @association.target
end

#third(*args) ⇒ Object

Same as first except returns only the third record.


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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 180

def third(*args)
  @association.third(*args)
end

#to_aryObject Also known as: to_a

Returns a new array of objects from the collection. If the collection hasn't been loaded, it fetches the records from the database.

class Person < ActiveRecord::Base
  has_many :pets
end

person.pets# => [
#       #<Pet id: 4, name: "Benny", person_id: 1>,
#       #<Pet id: 5, name: "Brain", person_id: 1>,
#       #<Pet id: 6, name: "Boss",  person_id: 1>
#    ]


other_pets = person.pets.to_ary# => [
#       #<Pet id: 4, name: "Benny", person_id: 1>,
#       #<Pet id: 5, name: "Brain", person_id: 1>,
#       #<Pet id: 6, name: "Boss",  person_id: 1>
#    ]


other_pets.replace([Pet.new(name: 'BooGoo')])

other_pets# => [#<Pet id: nil, name: "BooGoo", person_id: 1>]


person.pets# This is not affected by replace
# => [
#       #<Pet id: 4, name: "Benny", person_id: 1>,
#       #<Pet id: 5, name: "Brain", person_id: 1>,
#       #<Pet id: 6, name: "Boss",  person_id: 1>
#    ]


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# File 'activerecord/lib/active_record/associations/collection_proxy.rb', line 944

def to_ary
  load_target.dup
end