Alright, folks, let’s have a little chat about an absolutely nifty tool for all you developers out there who are diving into the realm of user roles and logins. Imagine you’re an admin or dev, and you need to peek into a user’s account without logging out and back in a hundred times. Sounds like a hassle, right? Well, say hello to your new best friend: the devise_masquerade gem! This gem will become your go-to for logging in as another user while staying cozy in your current session. Let’s roll through the steps to get this beauty integrated into your Ruby on Rails application.

First thing’s first. We gotta install this gem. Open up your Gemfile and drop this line in there:

gem 'devise_masquerade'

Save it, and then head over to your terminal and type:

bundle install

And boom! The gem is in the house.

Next up, we need to tweak your user model to make the gem work its magic. Pop open your user model file, usually lounging at app/models/user.rb, and add :masqueradable to the usual suspects list:

class User < ApplicationRecord
  devise :invitable, :confirmable, :database_authenticatable, :registerable, :masqueradable
end

Alright, that was easy-peasy. Now, let’s get your controllers ready. Head over to your app/controllers/application_controller.rb file. You’ll sprinkle a bit of masquerade magic here by adding this before action:

class ApplicationController < ActionController::Base
  before_action :masquerade_user!

  private

  def masquerade_user!
    if session[:masquerade_user_id]
      sign_in(:user, User.find(session[:masquerade_user_id]), bypass: true)
      session[:original_user_id] = current_user.id
      session[:original_user_class] = current_user.class.name
    end
  end

  def back_masquerade_path(user)
    if user_masquerade?
      session[:original_user_id]
    end
  end

  def user_masquerade?
    session[:original_user_id].present?
  end

  def back_masquerade
    if user_masquerade?
      original_user = User.find(session[:original_user_id])
      sign_in(:user, original_user, bypass: true)
      session[:masquerade_user_id] = nil
      session[:original_user_id] = nil
      session[:original_user_class] = nil
    end
  end
end

Sweet, your controllers are looking good. Now, let’s add some links to your views to activate the “Login As” magic. In your admin views, add something like this:

<% if policy(@user).masquerade? %>
  <%= link_to "Login as", masquerade_path(@user) %>
<% end %>

These links will hook up to the masquerade URLs neatly.

To keep things secure, you gotta ensure only the right folks can play around with this. Create a custom masquerades controller, like so:

class Admin::MasqueradesController < Devise::MasqueradesController
  protected

  def masquerade_authorize!
    authorize!(:masquerade, User)
  end
end

This little piece makes sure that only users with the right permissions can ride the masquerade train.

You’re almost there! To let users know they are currently masquerading, add a nifty alert in your views like this:

<% if user_masquerade? %>
  <div class="alert alert-warning text-center" style="margin-bottom: 0px">
    You're logged in as <%= current_user.name %>.
    <%= link_to "Back to original user", back_masquerade_path(current_user) do %>
      Logout <%= fa_icon "times" %>
    <% end %>
  </div>
<% end %>

This heads-up will keep things clear for your masquerading users.

Now, some heads-up about potential hiccups:

When you’re on development mode, caching issues might rear their ugly head. You may see errors like “You are already signed in.” Don’t panic. Enable caching by running:

rails dev:cache

This might save you tons of headaches.

And if you’re working with different subdomains, managing sessions and cookies becomes super crucial. Make sure your session store is set to share sessions across subdomains:

Rails.application.config.session_store :cookie_store, key: '_your_app_session', domain: :all

This ensures everything runs smoothly across subdomains.

So, there you have it. The devise_masquerade gem can truly make your life easier by allowing seamless switching between user roles without the constant log in-and-out shuffle. Follow these steps, and you’ll have it integrated into your Ruby on Rails application in no time.

Happy coding!