IoC and interface binding catch 22 - php

Question

So in trying to implement IoC, DI, etc. in Laravel 4, I've hit a wall. Either I'm misunderstanding something or doing something horribly wrong, not sure which...
So I have a class Person ("business class", not a model or library):
namespace Entities;
use Interfaces\Person as PersonInterface;
class Person implements PersonInterface {...}
a factory which has:
use Interfaces\Person;
...
App::singleton('user', function($app) {
...
$user_object = new Person();
...
});
and in the aliases array:
'Interfaces\Person' => 'Entities\Person'
Problem is that doesn't work because the Person class can't implement its interface because the interface is bound back to the Person class:
Entities\Person cannot implement Entities\Person - it is not an interface
I seem to be caught in a catch 22 of using IoC and interfaces in the application preventing the classes from actually instantiating.
Don't know if it's relevant, but putting
App::bind('Interfaces\Person','Entities\Person');
in the routes.php files doesn't seem to do anything (but putting it in the aliases array does). Surely I'm doing something wrong here. Any ideas?

Answer 1

Maybe I can help. To bind an interface to the IoC, you want to have an interface and an implementation of the interface. It looks like you have that step correct. You also want to create a service provider. More info on that here: http://laravel.com/docs/ioc#service-providers
Remove any bindings you have from the routes.php file. The service provider is what binds the route, and config/app.php registers it in the IoC as described more fully below.
Your service provider might look something like this:
File Name: ServiceProviders/PersonServiceProvider.php
<?php namespace ServiceProviders;
use Illuminate\Support\ServiceProvider;
use Entities\Person;
class PersonServiceProvider extends ServiceProvider {
/**
* Register the binding.
*
* #return void
*/
public function register()
{
$this->app->bind('Interfaces\Person', function()
{
return new Person();
});
}
}
Once the service provider is created, register it in the config/app.php file as follows:
'ServiceProviders\PersonServiceProvider',
Don't use the aliases. This is used for registering the aliases of facades, which is not what you're attempting to do here if I understand your question correctly.
Lastly, to follow the generally accepted Laravel naming conventions, I'd suggest naming the interface file "PersonInterface.php" and its interface "interface PersonInterface." Similarly, the implementation file might be called "EloquentPerson.php" and the "class EloquentPerson extends PersonInterface". This assumes you're using Eloquent. It's similar to what you have, but I think the class and interface names could make it more readable with those small tweaks.