class ActiveRecord::Associations::CollectionProxy

def delete(*records)

# ]
# #
# #,
# => [
person.pets.delete(2, 3)

# => [#]
person.pets.delete("1")

# ]
# #
# #,
# #,
# => [
person.pets
person.pets.size # => 3

end
has_many :pets
class Person < ActiveRecord::Base

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

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

# ]
# #
# #,
# => [
person.pets
person.pets.size # => 2

# => [#]
person.pets.delete(Pet.find(1))

# ]
# #
# #,
# #,
# => [
person.pets
person.pets.size # => 3

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

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

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

# => [#]
person.pets
person.pets.size # => 1

# ]
# #
# #,
# => [
person.pets.delete(Pet.find(1), Pet.find(3))

# ]
# #
# #,
# #,
# => [
person.pets
person.pets.size # => 3

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

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

# => #
Pet.find(1)

# ]
# #
# #,
# => [
person.pets
person.pets.size # => 2

# => [#]
person.pets.delete(Pet.find(1))

# ]
# #
# #,
# #,
# => [
person.pets
person.pets.size # => 3

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

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

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

deleted records.
then it will follow the default strategy. Returns an array with the
specified by the +:dependent+ option. If no +:dependent+ option is given,
Deletes the +records+ supplied from the collection according to the strategy 
def delete(*records)
  @association.delete(*records).tap { reset_scope }
end