Last night Mike was adding a feature to the Cultural Awards 2008 website where an admin could manually create a new user with any validly formatted email address, different to the public user registration where users can only use nsw.gov.au email addresses when registering.

One approach to solving this might be to store a global “current user” from a controller’s before/around filter which you’d then check when performing validations. I don’t particularly like this approach for the simple problem at hand because it pushes the request/response state into the model and makes the interaction between model objects less explicit.

My preferred method would be to simply have the creator of the User object specify the state under which validation should occur, and the simplest way to accomplish this is with an accessor method and the validation conditional options :if and :unless.

Below we’ll use :if and :unless to specify an instance method defining whether we perform this validation or not. The controller simply sets the flag on the model before requesting validation.

class User < ActiveRecord::Base
  attr_accessor :validate_as_admin
  attr_protected :validate_as_admin # Protect from mass-assignment

  validates_format_of :email,
                      :with => Format::NSW_GOV_EMAIL,
                      :unless => :validate_as_admin,
                      :message => "is not a valid nsw.gov.au address" 

  validates_format_of :email,
                      :with => Format::EMAIL,
                      :if => :validate_as_admin,
                      :message => "is not a valid email address" 
end

The existing public user registration doesn’t need to change:

class UsersController < ApplicationController
  def create
    @user = User.new(params[:user])
    # @user.validate_as_admin == nil by default
    @user.save!
    redirect_to members_path
  rescue ActiveRecord::RecordInvalid
    render :action => "new" 
  end
end

The admin section now simply sets validate_as_admin = true before triggering the validation:

class Admin::UsersController < Admin::BaseController
  def create
    @user = User.new(params[:user])
    @user.validate_as_admin = true
    @user.save!
    redirect_to members_path
  rescue ActiveRecord::RecordInvalid
    render :action => "new" 
  end
end

and that’s it.

It’s a similar technique we used when creating simple step-based validation.

If the problem you’re solving is more complex then you may consider using Jay Field’s excellent Validatable plugin which does a whole bunch of things, one of which is validation grouping.