class ActiveRecord::Associations::CollectionProxy - activerecord-4.2.5.2 Documentation

# class ActiveRecord::Associations::CollectionProxy

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.

### Public Instance Methods

<<(*records) click to toggle source

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>
    #    ]

    # File lib/active_record/associations/collection_proxy.rb, line 969
    def <<(*records)
      proxy_association.concat(records) && self
    end

Also aliased as: push, append
==(other) click to toggle source

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

    # File lib/active_record/associations/collection_proxy.rb, line 907
    def ==(other)
      load_target == other
    end

any?(&block) click to toggle source

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

    # File lib/active_record/associations/collection_proxy.rb, line 805
    def any?(&block)
      @association.any?(&block)
    end

append(*records)
Alias for: <<
arel() click to toggle source

    # File lib/active_record/associations/collection_proxy.rb, line 861
    def arel
      scope.arel
    end

build(attributes = {}, &block) click to toggle source

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

    # File lib/active_record/associations/collection_proxy.rb, line 258
    def build(attributes = {}, &block)
      @association.build(attributes, &block)
    end

Also aliased as: new
clear() click to toggle source

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.

    # File lib/active_record/associations/collection_proxy.rb, line 982
    def clear
      delete_all
      self
    end

concat(*records) click to toggle source

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

    # File lib/active_record/associations/collection_proxy.rb, line 333
    def concat(*records)
      @association.concat(*records)
    end

count(column_name = nil, options = {}) click to toggle source

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>
    #    ]

    # File 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) click to toggle source

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>
    #    ]

    # File lib/active_record/associations/collection_proxy.rb, line 289
    def create(attributes = {}, &block)
      @association.create(attributes, &block)
    end

create!(attributes = {}, &block) click to toggle source

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

    # File lib/active_record/associations/collection_proxy.rb, line 305
    def create!(attributes = {}, &block)
      @association.create!(attributes, &block)
    end

delete(*records) click to toggle source

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 `Fixnum` 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>
    #    ]

    # File lib/active_record/associations/collection_proxy.rb, line 588
    def delete(*records)
      @association.delete(*records)
    end

delete_all(dependent = nil) click to toggle source

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

    # File lib/active_record/associations/collection_proxy.rb, line 442
    def delete_all(dependent = nil)
      @association.delete_all(dependent)
    end

destroy(*records) click to toggle source

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 `Fixnum` 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)

    # File lib/active_record/associations/collection_proxy.rb, line 660
    def destroy(*records)
      @association.destroy(*records)
    end

destroy_all() click to toggle source

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

    # File lib/active_record/associations/collection_proxy.rb, line 469
    def destroy_all
      @association.destroy_all
    end

distinct() click to toggle source

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">]

    # File lib/active_record/associations/collection_proxy.rb, line 678
    def distinct
      @association.distinct
    end

Also aliased as: uniq
empty?() click to toggle source

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

    # File lib/active_record/associations/collection_proxy.rb, line 772
    def empty?
      @association.empty?
    end

fifth(*args) click to toggle source

Same as `first` except returns only the fifth record.

    # File lib/active_record/associations/collection_proxy.rb, line 190
    def fifth(*args)
      @association.fifth(*args)
    end

find(*args, &block) click to toggle source

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>
    #    ]

    # File lib/active_record/associations/collection_proxy.rb, line 140
    def find(*args, &block)
      @association.find(*args, &block)
    end

first(*args) click to toggle source

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) # => []

    # File lib/active_record/associations/collection_proxy.rb, line 170
    def first(*args)
      @association.first(*args)
    end

forty_two(*args) click to toggle source

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

    # File lib/active_record/associations/collection_proxy.rb, line 196
    def forty_two(*args)
      @association.forty_two(*args)
    end

fourth(*args) click to toggle source

Same as `first` except returns only the fourth record.

    # File lib/active_record/associations/collection_proxy.rb, line 185
    def fourth(*args)
      @association.fourth(*args)
    end

include?(record) click to toggle source

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

    # File lib/active_record/associations/collection_proxy.rb, line 857
    def include?(record)
      !!@association.include?(record)
    end

last(*args) click to toggle source

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) # => []

    # File lib/active_record/associations/collection_proxy.rb, line 226
    def last(*args)
      @association.last(*args)
    end

length() click to toggle source

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>
    #    ]

    # File lib/active_record/associations/collection_proxy.rb, line 750
    def length
      @association.length
    end

load_target() click to toggle source

    # File lib/active_record/associations/collection_proxy.rb, line 44
    def load_target
      @association.load_target
    end

loaded?() click to toggle source

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

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

    # File lib/active_record/associations/collection_proxy.rb, line 53
    def loaded?
      @association.loaded?
    end

many?(&block) click to toggle source

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

    # File lib/active_record/associations/collection_proxy.rb, line 843
    def many?(&block)
      @association.many?(&block)
    end

new(attributes = {}, &block)
Alias for: build
prepend(*args) click to toggle source

    # File 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_association() click to toggle source

    # File lib/active_record/associations/collection_proxy.rb, line 865
    def proxy_association
      @association
    end

push(*records)
Alias for: <<
reload() click to toggle source

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>]

    # File lib/active_record/associations/collection_proxy.rb, line 1005
    def reload
      proxy_association.reload
      self
    end

replace(other_array) click to toggle source

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

    # File lib/active_record/associations/collection_proxy.rb, line 359
    def replace(other_array)
      @association.replace(other_array)
    end

reset() click to toggle source

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>]

    # File lib/active_record/associations/collection_proxy.rb, line 1026
    def reset
      proxy_association.reset
      proxy_association.reset_scope
      self
    end

scope() click to toggle source

Returns a `Relation` object for the records in this association

    # File lib/active_record/associations/collection_proxy.rb, line 878
    def scope
      @association.scope
    end

Also aliased as: spawn
scoping() { || ... } click to toggle source

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.

    # File lib/active_record/associations/collection_proxy.rb, line 873
    def scoping
      @association.scope.scoping { yield }
    end

second(*args) click to toggle source

Same as `first` except returns only the second record.

    # File lib/active_record/associations/collection_proxy.rb, line 175
    def second(*args)
      @association.second(*args)
    end

select(*fields, &block) click to toggle source

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">
    #    ]

    # File lib/active_record/associations/collection_proxy.rb, line 110
    def select(*fields, &block)
      @association.select(*fields, &block)
    end

size() click to toggle source

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.

    # File lib/active_record/associations/collection_proxy.rb, line 726
    def size
      @association.size
    end

spawn()
Alias for: scope
take(n = nil) click to toggle source

    # File lib/active_record/associations/collection_proxy.rb, line 230
    def take(n = nil)
      @association.take(n)
    end

target() click to toggle source

    # File lib/active_record/associations/collection_proxy.rb, line 40
    def target
      @association.target
    end

third(*args) click to toggle source

Same as `first` except returns only the third record.

    # File lib/active_record/associations/collection_proxy.rb, line 180
    def third(*args)
      @association.third(*args)
    end

to_a()
Alias for: to_ary
to_ary() click to toggle source

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>
    #    ]

    # File lib/active_record/associations/collection_proxy.rb, line 944
    def to_ary
      load_target.dup
    end

Also aliased as: to_a
uniq()
Alias for: distinct