Rails: how to disable before_destroy callback when it's being destroyed because of the parent is being destroyed (:dependent => :destroy)

Question

I have two classes: Parent and Child with

Child:

belongs_to :parent 

and

Parent

has_many :children, :dependent => :destroy 

The problem is that I want to check that there is always at least one child present, so I have a before_destroy method in Child that abort the destroy if it is the only child belonging to its parent.

And, if I want to destroy the parent, it will call the before_destroy callback on every child, but when there is one child, it will abort the destroy, so the parent will never get destroyed.

How can I tell the child to call the before_destroy callback only if it's not being destroyed because of its parent?

Thanks!

Answer 1

In Rails 4 you can do the following:

class Parent < AR::Base   has_many :children, dependent: :destroy end  class Child < AR::Base   belongs_to :parent    before_destroy :check_destroy_allowed, unless: :destroyed_by_association    private    def check_destroy_allowed     # some condition that returns true or false   end end 

This way, when calling destroy directly on a child, the check_destroy_allowed callback will be run, but when you call destroy on the parent, it won't.

Answer 2

has_many :childs, :dependent => :delete_all 

This will delete all the children without running any hooks.

You can find the documentation at: http://api.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html#method-i-has_many