How to remove validation using instance_eval clause in Rails?

Question

I would like to enhance existing class using instance_eval. There original definition contains validation, which require presence of certain fields, ie:

class Du         


        

Answer 1

I found a solution, not sure how solid it is, but it works well in my case. @aVenger was actually close with his answer. It's just that the _validators accessor contains only information used for reflection, but not the actual validator callbacks! They are contained in the _validate_callbacks accessor, not to be confused with _validations_callbacks.

Dummy.class_eval do
  _validators.reject!{ |key, _| key == :field }

  _validate_callbacks.reject! do |callback|
    callback.raw_filter.attributes == [:field]
  end
end

This will remove all validators for :field. If you want to be more precise, you can reject the specific validator for _validators which is the same as the raw_filter accessor of validate callbacks.

Answer 2

If you can edit the constraint on the original model to put an :if => :some_function on it, you can easily change the behavior of the function it calls to return false. I tested this and it works pretty easily:

class Foo < ActiveRecord::Base

  validates :field, :presence => true, :if => :stuff


  attr_accessor :field

  def stuff
      return true;
  end

end

and then somewhere else:

Foo.class_eval {
  def stuff
    false
  end
}

Answer 3

As I was trying to do this to remove the phone validation from the spree Address model, below is the code I got to work. I added the type check for callback.raw_filter because I only wanted to remove the presence validator on the phone field. I also had to add it because it would fail when trying to run against one of the other validators specified in the Spree::Address model that did not have an 'attributes' key for callback.raw_filter, thus an exception was thrown.

Spree::Address.class_eval do

   # Remove the requirement on :phone being present.
  _validators.reject!{ |key, _| key == :phone }

  _validate_callbacks.each do |callback|
    callback.raw_filter.attributes.delete :phone if callback.raw_filter.is_a?(ActiveModel::Validations::PresenceValidator)
  end

end

Answer 4

Why not use @dummy.save_without_validation method to skip validations altogether? I prefer do something like this:

if @dummy.valid?
  @dummy.save # no problem saving a valid record
else
  if @dummy.errors.size == 1 and @dummy.errors.on(:field)
    # skip validations b/c we have exactly one error and it is the validation that we want to skip
    @dummy.save_without_validation 
  end
end

You could put this code in your model or in the controller, depending on your needs.

Answer 5

If you really want to do this then here would be a good place to start digging: https://github.com/rails/rails/blob/ed7614aa7de2eaeba16c9af11cf09b4fd7ed6819/activemodel/lib/active_model/validations/validates.rb#L82

However, to be honest, inside of ActiveModel is not where I'd be poking with a stick.

Answer 6

I had a similar problem and was able to get past it using:

class MyModel << Dummy
  # erase the validations defined in the plugin/gem because they interfere with our own
  Dummy.reset_callbacks(:validate)
  ...
end

This is under Rails 3.0. The caveat: It does remove ALL validations, so if there are others you want to keep you could try Dummy.skip_callback(...), but I could not figure out the right incantation of arguments to make that work.