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in leveraging regular Ruby classes and object oriented design patterns to build a simple, robust and scaleable authorization system

map to the name of a particular controller action

In the generated ApplicationPolicy, the model object is called record.

record

authorize

authorize would have done something like this: raise "not authorized" unless PostPolicy.new(current_user, @post).update?

pass a second argument to authorize if the name of the permission you want to check doesn't match the action name.

you can chain it

authorize returns the object passed to it

the policy method in both the view and controller.

have some kind of view listing records which a particular user has access to

ActiveRecord::Relation

Instances of this class respond to the method resolve, which should return some kind of result which can be iterated over.

scope.where(published: true)

use this class from your controller via the policy_scope method:

PostPolicy::Scope.new(current_user, Post).resolve

policy_scope(@user.posts).each

This method will raise an exception if authorize has not yet been called.

verify_policy_scoped to your controller. This will raise an exception in the vein of verify_authorized. However, it tracks if policy_scope is used instead of authorize

need to conditionally bypass verification, you can use skip_authorization

skip_policy_scope

Having a mechanism that ensures authorization happens allows developers to thoroughly test authorization scenarios as units on the policy objects themselves.

Pundit doesn't do anything you couldn't have easily done yourself. It's a very small library, it just provides a few neat helpers.

all of the policy and scope classes are just plain Ruby classes

rails g pundit:policy post

define a filter that redirects unauthenticated users to the login page

fail more gracefully

raise Pundit::NotAuthorizedError, "must be logged in" unless user

having rails handle them as a 403 error and serving a 403 error page.

config.action_dispatch.rescue_responses["Pundit::NotAuthorizedError"] = :forbidden

with I18n to generate error messages

retrieve a policy for a record outside the controller or view

define a method in your controller called pundit_user

Pundit strongly encourages you to model your application in such a way that the only context you need for authorization is a user object and a domain model that you want to check authorization for.

Pundit does not allow you to pass additional arguments to policies

set up a permitted_attributes method in your policy

policy(@post).permitted_attributes

permitted_attributes(@post)

Pundit provides a convenient helper method

permit different attributes based on the current action,

If you have defined an action-specific method on your policy for the current action, the permitted_attributes helper will call it instead of calling permitted_attributes on your controller

If you don't have an instance for the first argument to authorize, then you can pass the class

It is not some kind of failsafe mechanism or authorization mechanism.

Pundit will work just fine without using verify_authorized and verify_policy_scoped