I'm building a small app with Rails 4.2.6. Suppose I have the following classes:
class Caseworker < ActiveRecord::Base
has_many :cases
end
class Case < ActiveRecord::Base
belongs_to :caseworkers
end
... with views to create, view, update, and destroy them each. I then create multiple Caseworkers and assign multiple Cases to them.
Currently, if I attempt to delete a Caseworker, I'll get an error:
Mysql2::Error: Cannot delete or update a parent row: a foreign key constraint fails
No problem, that's to be expected.
In some CMSes, though, if a user
attempts to destroy an object with such dependencies, you can present
them with the option to assign the objects to another parent, or
destroy them. Is there a standard way, in Rails, to offer this functionality? Otherwise, it seems like I will need to put a before_destroy clause in the Caseworker controller... is this true? I'm not afraid to write such a method if need be, but I'd rather not reinvent this wheel if it's there for me to use somewhere.
You can add one of dependent: :destroy or dependent: :nullify to the has_many statement, depending on whether you want the children deleted or to have their foreign key field nulled.
For example, to delete the Cases belonging to a Caseworker being deleted you could use:
class Caseworker < ActiveRecord::Base
has_many :cases, dependent: :destroy
end
To my knowledge Rails has no way to reassign children to a different parent - you'd have to write code to do that yourself.