Laravel Target is not instantiable while building - php

Question

I created an Artisan command which worked and where I injected a Kafka client service as the first parameter and a concrete class BudgetsTransformer, as the second parameter.
class ConsumeBudgetsCommand extends Command {
public function __construct(FKafka $kafkaClient, BudgetsTransformer $transformer)
{
$this->kafkaClient = $kafkaClient;
$this->transformer = $transformer;
parent::__construct();
}
}
AppServiceProvider class looked like:
class AppServiceProvider extends ServiceProvider
{
public function register()
{
$this->app->bind('kafka.client', function ($app) {
return new \Weq\FKafka\FKafka();
});
$this->app->bind('budget.transformer', function ($app) {
return new BudgetsTransformer();
});
}
public function boot()
{
$this->app->bind('consume:budgets', function ($app) {
return new ConsumeBudgetsCommand($app['kafka.client'], $app['budget.transformer']);
});
$this->commands('consume:budgets');
}
}
So far all is working properly. Then I decided to create a TransformerInterface which BudgedTransformer implements (and other future Transformers will implement it):
class BudgetsTransformer implements TransformerInterface
{
// ...
}
and I changed the signature in the command to inject the interface instead of the concrete class:
class ConsumeBudgetsCommand extends Command {
public function __construct(FKafka $kafkaClient, TransformerInterface $transformer)
{
$this->kafkaClient = $kafkaClient;
$this->transformer = $transformer;
parent::__construct();
}
}
But I get the following issue when I try to run some artisan command
In Container.php line 933:
Target [App\Transformers\TransformerInterface] is not instantiable while building [App\Console\Commands\ConsumeBudgetsCommand].
I run previously the issue the following artisan command just in case. cache:clear, clear-compiled, optimize and so on but no luck.
What I'm doing wrong? Should I bind the BudgetTransformer in a different way I'm doing now for passing and Interface instead of a concrete class?
I added:
$this->app->bind(TransformerInterface::class, BudgetsTransformer::class);
in AppServiceProvider::register() and I removed
$this->app->bind('budget.transformer', function ($app) {
return new BudgetsTransformer();
});
there, then I update in AppServiceProvider::boot() the command binding:
$this->app->bind('consume:budgets', function ($app) {
return new ConsumeBudgetsCommand($app['kafka.client'], $app[TransformerInterface::class]);
});
But still not working, anyway this approach (even working) will not resolve the issue since when I want to add another different transformer implementation, let's say CostTransformer which implements TransformerInterface is gonna always inject BudgetTransformer. So reading the documentation in the link, I found that Contextual Binding could be the solution, so I substituted by:
$this->app
->when(ConsumeBudgetsCommand::class)
->needs(TransformerInterface::class)
->give(function ($app) {
return new BudgetsTransformer();
});
So in that way, I will be able to inject different implementations of transformers to different commands by injecting the interface. But still not working.
Can someone tell me how exactly declare the command binding
$this->app->bind('consume:budgets', function ($app) {
return new ConsumeBudgetsCommand($app['kafka.client'], ???);
});
to use that Contextual binding?

Answer 1

For binding interfaces must be use this structure https://laravel.com/docs/5.5/container#binding-interfaces-to-implementations
$this->app->bind(TransformerInterface::class, BudgetsTransformer::class);
And
$this->app->bind('consume:budgets', function ($app) {
return new ConsumeBudgetsCommand($app['kafka.client'], $app->make(TransformerInterface::class));
});