Bad
# Given the following models
class Image < ActiveRecord::Base
has_many :album_images
has_many :albums, through: :album_images
end
class Album < ActiveRecord::Base
has_many :album_images
has_many :images, through: :album_images
end
# Join model
class AlbumImage < ActiveRecord::Base
belongs_to :album
belongs_to :image
end
Destroying a record in this setup will only remove the record itself, and leave orphaned join records behind.
image = Image.last
image.destroy # removes only the `image` record,
# but none of the associated `album_image` join records
Good
By adding the :dependent => :destroy option to the has_many :through associations, the join records will be removed when an image or an album is destroyed.
class Image < ActiveRecord::Base
has_many :album_images
has_many :albums, through: :album_images, dependent: :destroy
end
class Album < ActiveRecord::Base
has_many :album_images
has_many :images, through: :album_images, dependent: :destroy
end
Note: the associated record with through (the albums in the example) will never be deleted by specifying dependent: :destroy, only the join records. Thus the following example will have the same effect as the above and is more explicit:
class Image < ActiveRecord::Base
has_many :album_images, dependent: :destroy
has_many :albums, through: :album_images
end
Posted to makandra dev (2015-04-17 12:18)