Laravel service provider explanation - php

Question

I'm not much familiar with Laravel Service provider and I have a question about it.
Example: I have three classes SystemProfiler, SurveyProfiler and OfferProfiler which implements ProfilerInterface. And also I have ProfilerService class which inject ProfilerInterface in the constructor. I need to create different ProfilerService services with injection of each of that profilers.
ProfilerService:
class ProfilerService {
$this->profiler;
function __construct(ProfilerInterface $profiler) {
$this->profiler = profiler;
}
}
I know how to do that in symfony2 framework:
system_profiler:
class: App\MyBundle\Profiles\SystemProfiler
survey_profiler:
class: App\MyBundle\Profiles\SurveyProfiler
offer_profiler:
class: App\MyBundle\Profiles\OfferProfiler
system_profile_service:
class: App\MyBundle\Services\ProfilerService
arguments:
- system_profiler
survey_profile_service:
class: App\MyBundle\Services\ProfilerService
arguments:
- survey_profiler
offer_profile_service:
class: App\MyBundle\Services\ProfilerService
arguments:
- offer_profiler
and then just call $this->container->get() with alias of ProfilerService realization
But Laravel documentation said that "there is no need to bind classes into the container if they do not depend on any interfaces.". And ProfilerService not depend on interface. So I can bind each profiler to interface like so:
$this->app->bind('App\MyBundle\Contracts\ProfilerInterface','App\MyBundle\Profiles\SystemProfiler');
or
$this->app->bind('App\MyBundle\Contracts\ProfilerInterface','App\MyBundle\Profiles\SurveyProfiler');
or
$this->app->bind('App\MyBundle\Contracts\ProfilerInterface','App\MyBundle\Profiles\OfferProfiler');
but how I should bind which of the Profilers should be injected to the ProfilerService and when???
I would appreciate any help and explanations

Answer 1

Here it goes (read the docs):
// ServiceProvider
public function register()
{
// Simple binding
$this->app->bind('some_service.one', \App\ImplOne::class);
$this->app->bind('some_service.two', \App\ImplTwo::class);
// Aliasing interface - container will inject some_service.one
// whenever interface is required...
$this->app->alias('some_service.one', \App\SomeInterface::class);
// ...except for the Contextual Binding:
$this->app->when(\App\DependantTwo::class)
->needs(\App\SomeInterface::class)
->give('some_service.two');
}
USAGE:
$ php artisan tinker
// Aliases
>>> app('some_service.one')
=> App\ImplOne {#669}
>>> app('some_service.two')
=> App\ImplTwo {#671}
// Aliased interface
>>> app('App\SomeInterface')
=> App\ImplOne {#677}
>>> app('App\DependantOne')->dependency
=> App\ImplOne {#677}
// Contextual
>>> app('App\DependantTwo')->dependency
=> App\ImplOne {#676}
Given this setup:
namespace App;
class ImplOne implements SomeInterface {}
class ImplTwo implements SomeInterface {}
class DependantOne
{
public function __construct(SomeInterface $dependency)
{
$this->dependency = $dependency;
}
}
class DependantTwo
{
public function __construct(SomeInterface $dependency)
{
$this->dependency = $dependency;
}
}

Answer 2

The constructor of your ProfilerService typehints an interface, which means that your ProfilerService does depend on an interface.
Without any additional setup, if you attempted to App::make('App\MyBundle\Services\ProfilerService');, you would get an error because Laravel wouldn't know how to resolve the interface dependency.
When you then do $this->app->bind('App\MyBundle\Contracts\ProfilerInterface','App\MyBundle\Profiles\SystemProfiler'); in your service provider, you're telling Laravel "whenever you need to resolve a ProfilerInterface, create a new SystemProfiler".
With that binding setup, if you then attempted to App::make('App\MyBundle\Services\ProfilerService');, Laravel would create a new ProfilerService instance, and inject a new SystemProfiler instance in the constructor.
However, this isn't exactly what you want, since you have three different implementations of the ProfilerInterface. You don't want Laravel always injecting just one. In this case, you would create custom bindings, similar to what you've done in Symfony.
In your service provide, your bindings would look something like this:
$this->app->bind('system_profile_service', function($app) {
return $app->make('App\MyBundle\Services\ProfilerService', [$app->make('App\MyBundle\Profiles\SystemProfiler')]);
});
$this->app->bind('survey_profile_service', function($app) {
return $app->make('App\MyBundle\Services\ProfilerService', [$app->make('App\MyBundle\Profiles\SurveyProfiler')]);
});
$this->app->bind('offer_profile_service', function($app) {
return $app->make('App\MyBundle\Services\ProfilerService', [$app->make('App\MyBundle\Profiles\OfferProfiler')]);
});
Now, with those bindings setup, you resolve your custom bindings from the IOC whenever you need one.
$systemProfiler = App::make('system_profiler_service');
$surveyProfiler = App::make('survey_profile_service');
$offerProfiler = App::make('offer_profile_service');