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

Answer by aVenger has problems when you declare validations of more than one attribute in a line:

validates :name, :message, :presence => true

That's because this line creates a raw_filter with more than one attribute in attributes filter:

Model.send(:_validate_callbacks)
=> [#, @filter="_callback_before_75", @compiled_options="true", @callback_id=76>]

We have to delete the desired attribute from that array and reject the callbacks without attributes

Dummy.class_eval do

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

  _validate_callbacks.each do |callback|
    callback.raw_filter.attributes.delete :field
  end

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

I have this working on a Rails 3.2.11 app.