Action Policy

Usage

Action Policy relies on resource-specific policy classes (just like Pundit).

First, add an application-specific ApplicationPolicy with some global configuration to inherit from:

class ApplicationPolicy < ActionPolicy::Base
end

This may be done with the rails generate action_policy:install generator.

Then, write a policy for a resource. For example:

class PostPolicy < ApplicationPolicy
  # everyone can see any post
  def show?
    true
  end

  def update?
    # `user` is a performing subject,
    # `record` is a target object (post we want to update)
    user.admin? || (user.id == record.user_id)
  end
end

This may be done with the rails generate action_policy:policy Post generator.

Now you can easily add authorization to your Rails controller:

class PostsController < ApplicationController
  def update
    @post = Post.find(params[:id])
    authorize! @post

    if @post.update(post_params)
      redirect_to @post
    else
      render :edit
    end
  end
end

When the authorization is successful (i.e., the corresponding rule returns true), nothing happens, but in case of authorization failure ActionPolicy::Unauthorized an error is raised.

There is also an allowed_to? method which returns true or false, and could be used in views:

<% @posts.each do |post| %>
  <li><%= post.title %>
    <% if allowed_to?(:edit?, post) %>
      <%= link_to post, "Edit">
    <% end %>
  </li>
<% end %>

Read more in the Documentation.