constant_values.md

Constant values

Until now, you used the Stubbles IoC framework only to inject objects. However, it is also possible to inject constant values into objects. The following example shows how this can be done. Imagine you have a class that requires the connection parameters for a database:

class MyApplication {
    /**
     * @Named('dbParams')
     */
    public function __construct(private string $params) { }

    // ... other methods of the class
}

As in the examples before, you annotated the method that should be used to inject the database connection parameters with the @Named annotation. When injecting non-objects, the @Named annotation is required, as there is no type hint to identify the binding.

Now, all that's left to do is specify a binding for the constant dbParams:

$binder->bindConstant('dbParams')->to('mysql:host=localhost;dbname=test');

$injector = $binder->getInjector();
$app = $injector->getInstance(MyApplication::class);

The $injector will now return a configured instance of MyApplication with the $dbParams property set.

stubbles/ioc is not meant to replace your own configuration framework, but in some cases injecting constant values can be helpful or might even be a requirement for your application to work.

Injecting constants works everywhere where the @Named annotation can be applied.

It is also possible to retrieve single constant values directly from the binder:

$dbParams = $injector->getConstant('dbParams');