Rails: Validating association after save?

Question

I have a User model which has many roles. Roles contains a user_id field, which I want to validate_presence_of

The is

Answer 1

I think you can get around the validation problem if you change your code to look like this:

@user = User.new(params[:user])
@user.roles.new(:name => 'Peon') unless @user.has_roles?
if @user.save
  # ...

If that doesn't work, you could try changing you validation to this:

class Role < ActiveRecord::Base
  belongs_to :user
  validates :user_id, :presence => true, :unless => Proc.new() {|r| r.user}
end