Voters

We need to centralize this logic so that it can be reused in other places:

How? Well... it may look a bit weird at first. Remove all of this logic and replace it with: if (!$this->isGranted('MANAGE', $article)):

Hmm. I'm using the same isGranted() function as before. But instead of passing a role, I'm just "inventing" a string: MANAGE. It also turns out that isGranted() has an optional second argument: a piece of data that is relevant to making this access decision.

Don't worry - this will not magically work somehow. If you try it... yep!

Access denied.

Hello Voter System

Let me explain what's happening. Whenever you call isGranted, or one of the other functions like denyAccessUnlessGranted(), Symfony executes what's known as the "Voter system". Basically, it takes the string - MANAGE, or ROLE_ADMIN_ARTICLE - and it asks each voter:

Hey voter! Do you know how to decide whether or not the current user has this string - ROLE_ADMIN_ARTICLE or MANAGE?

In the core of Symfony, there are basically two voters by default: RoleVoter and AuthenticatedVoter. When you pass any string that starts with ROLE_, the RoleVoter says:

Ah, yea! I totally know how to determine if the user should have access!

Then, it checks to see if the User has that role and returns true or false. The other voter "abstains" - which means it doesn't vote - and so access is entirely granted or denied by that one voter.

When you pass any string that starts with IS_AUTHENTICATED_, like IS_AUTHENTICATED_FULLY, the other voters says:

Oh. This is me! I know how to check this!

And it returns true or false based on how authenticated the user is and which of those three IS_AUTHENTICATED_ strings we passed.

Adding our Custom Voter

The really cool thing is that we can add our own custom voters. Right now, when we call isGranted() with the string MANAGE, both voters say:

Hmm, no, we don't understand what this is

They both "abstain" from voting. And when nobody votes, access is denied by default. So our goal is clear: introduce a new voter that understands how to handle the string MANAGE and an Article object. By the way, up until now, I've been calling this MANAGE string a role... because it has usually started with ROLE_. But actually, it's generally called a "permission attribute". Some permission attributes are roles, but some are other strings handled by other voters.

Oh, and why did I choose the word MANAGE? I just made that up. If you need different permissions for edit, show and delete, you would use different attributes for each - like EDIT, SHOW, DELETE - and create a voter that can handle all of those. You'll see soon. My case is simpler: I'll use MANAGE for any operation on an Article - for example, for editing, deleting or publishing it.

Ok, let's finally create our voter!