When you’re working with Ruby on Rails, it’s really important to know the difference between authentication and authorization. This knowledge helps keep your applications safe.

Authentication

Authentication is all about figuring out who the user is.

Imagine this: when you log into your bank account, you type in your username and password. This step shows that you are really you.

In Rails, you can use tools called gems, like Devise or Authlogic, to help with authentication. Here’s a simple example:

class SessionsController < ApplicationController
  def create
    user = User.find_by(email: params[:email])
    if user&.authenticate(params[:password])
      session[:user_id] = user.id
      redirect_to root_path, notice: "Logged in!"
    else
      flash.now[:alert] = "Invalid email or password"
      render :new
    end
  end
end

In this piece of code, we check if the user’s information is correct. If it is, we save the user's ID in the session.

Authorization

After we know who the user is, we need to find out what they can do. This is where authorization comes into play.

For example, a regular user shouldn’t be able to do admin tasks. In Rails, you can manage authorization using tools like Pundit or CanCanCan. Here’s how to do it with Pundit:

class ArticlesController < ApplicationController
  before_action :authenticate_user!
  before_action :set_article, only: [:show, :edit, :update, :destroy]
  after_action :verify_authorized

  def update
    @article = Article.find(params[:id])
    authorize @article
    # update logic here
  end
end

In this example, the authorize method checks to see if the current user has the right to update the article.

Conclusion

So, in short, authentication is about proving who you are. Authorization is about figuring out what you can do once you’re recognized.

Both of these steps are very important for keeping your Rails application secure. When you understand these ideas, you can build strong and safe applications!