如何在Rails的实例上运行validates_presence_of？

Question

I would like to do the following from a library class?

class LibClass
  def create_user(provider)
    user = User.new
    if provider == "facebook"
      user.validates_presence_of :email
    else
      # dont validate presence of email
    end
  end
end

I am aware that I can do a self.validates_presence_of :email inside the User class, but I am in the library class and am not sure how to do this?

Answer 1

In your User model, you can create an accessor to toggle the validation on or off.

class User < ActiveRecord::Base
  attr_accessor :validate_email

  def validate_email?; validate_email == true; end

  validates_presenece_of :email, :if => validate_email?
end

You can turn the validation on by setting user.validate_email = true :

def create_user(provider)
  user = User.new
  if provider == "facebook"
    user.validate_email = true
  else
    user.validate_email = false
  end
end

To actually get the validations to run, you can call user.valid? and the hash user.errors will be populated with any validation errors.

Answer 2

validates_presence_of is a class method, not an instance method. In order to do what you want you'll have to do this:

user.class_eval {validates_presence_of :email }

but the validation will be set on the class, and will be on for all your users.