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.

Methods
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Instance Public methods
<<(*records)

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>
#    ]
Also aliased as: push, append

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 1054
def <<(*records)
  proxy_association.concat(records) && self
end
==(other)

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

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 988
def ==(other)
  load_target == other
end
any?()

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 # => 1
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

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 900
append(*records)
Alias for: <<
build(attributes = {}, &block)

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
Also aliased as: new

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 315
def build(attributes = {}, &block)
  @association.build(attributes, &block)
end
calculate(operation, column_name)

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 753
def calculate(operation, column_name)
  null_scope? ? scope.calculate(operation, column_name) : super
end
clear()

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. Note that because delete_all removes records by directly running an SQL query into the database, the updated_at column of the object is not changed.

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 1070
def clear
  delete_all
  self
end
concat(*records)

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

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 390
def concat(*records)
  @association.concat(*records)
end
count(column_name = nil, &block)

Count all records.

class Person < ActiveRecord::Base
  has_many :pets
end

# This will perform the count using SQL.
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>
#    ]

Passing a block will select all of a person's pets in SQL and then perform the count using Ruby.

person.pets.count { |pet| pet.name.include?('-') } # => 2

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 787
create(attributes = {}, &block)

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>
#    ]

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 346
def create(attributes = {}, &block)
  @association.create(attributes, &block)
end
create!(attributes = {}, &block)

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

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 362
def create!(attributes = {}, &block)
  @association.create!(attributes, &block)
end
delete(*records)

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 'id': (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>
#    ]

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 645
def delete(*records)
  @association.delete(*records)
end
delete_all(dependent = nil)

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: Couldn't find all Pets with 'id': (1, 2, 3)

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: Couldn't find all Pets with 'id': (1, 2, 3)

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 499
def delete_all(dependent = nil)
  @association.delete_all(dependent)
end
destroy(*records)

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 'id': (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 'id': (4, 5, 6)

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 717
def destroy(*records)
  @association.destroy(*records)
end
destroy_all()

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

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 526
def destroy_all
  @association.destroy_all
end
distinct(value = true)

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">]

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

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 748
empty?()

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

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 860
def empty?
  @association.empty?
end
fifth()

Same as first except returns only the fifth record.

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 205
find(*args, &block)

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>
#    ]

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 136
def find(*args, &block)
  @association.find(*args, &block)
end
first(limit = nil)

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) # => []

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 173
forty_two()

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

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 214
fourth()

Same as first except returns only the fourth record.

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 197
include?(record)

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

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 951
def include?(record)
  !!@association.include?(record)
end
last(limit = nil)

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) # => []

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 256
def last(limit = nil)
  load_target if find_from_target?
  super
end
length()

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>
#    ]

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 842
load_target()

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 43
def load_target
  @association.load_target
end
loaded?()

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

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

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 52
def loaded?
  @association.loaded?
end
many?()

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

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 941
new(attributes = {}, &block)
Alias for: build
pluck(*column_names)

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 757
def pluck(*column_names)
  null_scope? ? scope.pluck(*column_names) : super
end
prepend(*args)

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 1060
def prepend(*args)
  raise NoMethodError, "prepend on association is not defined. Please use <<, push or append"
end
proxy_association()

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 955
def proxy_association
  @association
end
push(*records)
Alias for: <<
reload()

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>]

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 1093
def reload
  proxy_association.reload
  reset_scope
end
replace(other_array)

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

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 416
def replace(other_array)
  @association.replace(other_array)
end
reset()

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>]

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 1114
def reset
  proxy_association.reset
  proxy_association.reset_scope
  reset_scope
end
scope()

Returns a Relation object for the records in this association

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 960
def scope
  @scope ||= @association.scope
end
second()

Same as first except returns only the second record.

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 181
second_to_last()

Same as first except returns only the second-to-last record.

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 230
select(*fields, &block)

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>
#    ]

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 110
size()

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.

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 811
def size
  @association.size
end
take(limit = nil)

Gives a record (or N records if a parameter is supplied) from the collection using the same rules as ActiveRecord::Base.take.

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.take # => #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>

person.pets.take(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.take    # => nil
another_person_without.pets.take(2) # => []

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 286
def take(limit = nil)
  load_target if find_from_target?
  super
end
target()

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 39
def target
  @association.target
end
third()

Same as first except returns only the third record.

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 189
third_to_last()

Same as first except returns only the third-to-last record.

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 222
to_a()
Alias for: to_ary
to_ary()

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>
#    ]
Also aliased as: to_a

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 1025
def to_ary
  load_target.dup
end
uniq()

Source: show | on GitHub 

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 749
def uniq
  load_target.uniq
end