Where to put business logic in Lumen?

Question

I am developing my first API with Lumen. Normally I am using services for separating business logic or reused code from the controllers and share it with other controllers.

How to do this with lumen? Where to put the services? I only see ServiceProviders to register these services but for me it's not clear where and how to define them.

Answer 1

Lumen and its big brother Laravel come with a service container, which handles the dependencies injection.

To resolve things out of the container, you may either type-hint the dependency you need on a class that is already automatically resolved by the container, such as a route Closure, controller constructor, controller method, middleware, event listener, or queued job. Or, you may use the app function from anywhere in your application:

$instance = app(Something::class);

That's for "resolving things out". Registering the "things" is what the service providers are for. A service provider is just a class that extends Illuminate\Support\ServiceProvider and binds interfaces or classes to concrete implementations. (Read the docs for a detail on how to write your own.)

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Example: Create some test route:

$app->get('/test', 'TestController@test');

and create the controller method, type-hinting a parameter:

public function test(DatabaseManager $dbm)
{
    dd($dbm);
}

You will see that the DatabaseManager interface is resolved to a concrete class, properly instantiated and configured with your DB config. That's because at some point the framework is calling a service provider which takes care of doing that.

Any custom providers you may want to include are set in /bootstrap/app.php like so:

$app->register(App\Providers\AuthServiceProvider::class);

(Otherwise if you ask for a class that hasn't been bound by a provider, the framework just injects a new instance of that class.)

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So, for this problem you probably want some repository class where you can encapsulate all database access.

Example:

// app/Repositories/ProductRepository.php
private $db;

public function __construct(DatabaseManager $dbm)
{
    $this->db = $dbm->connection();
}

public function findById($id)
{
    return $this->db->table('products')->where('id', '=', $id)->get();
}

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//routes.php
$app->get('products/{id}', 'ProductsController@show');

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//ProductsController.php
public function show(ProductRepository $repo, $id)
{
    $product = $repo->findById($id);
    dd($product);
}

It's interesting in this example that you call for a ProductRepository injection, and, since it has a DatabaseManager dependency, the framework handles the instantiation of both.

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I hope this begins to answer your question about managing business logic in service providers. I guess another typical use case is authorization handling. You can follow the docs on this subject after this intro.