How to remove validation using instance_eval clause in Rails?

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]  endend

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.

I think this is the most actual solution at this moment (I'm using rails 4.1.6):

# Common ninjaclass Ninja < ActiveRecord::Base  validates :name, :martial_art, presence: trueend# Wow! He has no martial skillsNinja.class_eval do  _validators[:martial_art]    .find { |v| v.is_a? ActiveRecord::Validations::PresenceValidator }    .attributes    .delete(:martial_art)end

Easest way to remove all validations:

clear_validators!