Proposals for the dependency injection container

[ghost]

Hi Arul,

I noticed your Scope class (and a thread on Stackoverflow where you introduce it). While it's a great idea to enable DI in RESTler, but in fact, the current solution has some issues.

• One of them is that it's not really DI, but service location that I can see being used in RESTler (Scope::get() is invoked 50+ times and Scope is effectively a static class). The following article highlights the disadvantages of the practice of service location: http://www.devtrends.co.uk/blog/how-not-to-do-dependency-injection-the-static-or-singleton-container.
• Another problem is that it's impossible to use a third party container which could instantiate our controllers/services (am I right?). I want to use PHP-DI: beside others, a huge advantage of it that it is compliant to a PHP-FIG-like standard for DI containers (https://github.com/container-interop/container-interop).

So it would be great to change the way RESTler uses DI. My "action plan" is the following:

• First, enable the usage of external containers, so that controllers/services could be instantiated by them. In my opinion, only container-interop compliant containers should be regarded.
• Then the Scope class could support the aforementioned standard, so it would become optional to use it or not.
• Finally it could be worth refactoring RESTler to use real DI (not service location).

If you are ok with my opinion, I could make a PR soon for the first step. But the second and the third ones need more time and effort to be developed, so I don't promise anything.

[ghost]

A slight clarification: maybe I missed the point about Scope: you have never stated that Restler internally uses DI. You only told that Scope can ALSO be used as a DI container. Sorry for my misunderstanding. That is why the first issue becomes only a notice. :)

[Arul-]

I will go through the above mentioned article and get back to you!

[Arul-]

I will definitely consider this on RC6

[ghost]

I sent a new pull request for this issue which is far better than the last one. Basically, I created a Container Interop-compliant adapter for the Scope class which can be used for instanting the API classes.

[matak]

i am still not sure how DI in restler works, can you help to understand? bcs how can i inject for example database connection to apiclass constructor when it is instantiated? also it would be nice to set dependencies in constructors of api classes, when this class will be instantiated it looks to contructor and inject the service which i need from my DI container, maybe you should look on this implementation

http://doc.nette.org/en/2.2/dependency-injection

[matak]

i think the problem is here
https://github.com/Luracast/Restler/blob/master/vendor/Luracast/Restler/Scope.php#L94
so it means that is imposible to inject any objects/services into constructor of created api class?

[Arul-]

It is possible to do dependency injection with Scope, here is how it is done!

Scope::register('My\Api\Something', function () {
    return new My\Api\Something(
        Scope::get('My\Dependency1'),
        Scope::get('My\Dependency2')
    );
});

After the above code somewhere before $restler->handle(). When class Something is requested it will be created with the above function.

[matak]

i understand your meaning but it is not solution for me, all dependencies i have to keep in some configuration outside of the classes, in nette/di you can do this

class XY {
   public function __construct(\DibiConnection $sql, \CacheStorage $cache) { ...
}

and the services sql and cache are automaticaly injected, also the deep injection is provided.

bcs the \CacheStorage also need injection of \FileStorage and \DibiConnection and etc. so my structure what i need is based on constructors of the services nowhere else, and if i change it so it is all i need to do

what do you think about that? just let the nette/di do all DI and all will be served automatically, what do you think?

[matak]

i wanted to say that in your example how i set dependencies of My\Dependency1 ?

[Arul-]

Scope::register('My\DependencyX', function () {
    return My\DependencyX::instance();
}
Scope::register('My\Dependency1', function () {
    return new My\Dependency1(
        Scope::get('My\DependencyX'),
    );
});
Scope::register('My\Api\Something', function () {
    return new My\Api\Something(
        Scope::get('My\Dependency1'),
        Scope::get('My\Dependency2')
    );
});

[Arul-]

You can use any other DI along with Scope, see the following pseudo code

Scope::register('My\Api\Something', function ()  {
    return nette/di['something'];
});

[matak]

nice, what about implement nette/di from scratch? this means i need configure all api classes

[matak]

as a workaround done

$apis = array('Api\Endpoints', 'Api\Documents');
foreach($apis as $apiClass) {
    Luracast\Restler\Scope::register($apiClass, function () use ($context, $apiClass)  {
        return $context->getByType($apiClass);
    }); 
}

$r = new Restler(Debugger::DETECT); // return true if you are in production mode
$r->setSupportedFormats('JsonFormat', 'XmlFormat'); //from restler framework for API Explorer
$r->addAPIClass('Luracast\Restler\Resources');

//setup apis
foreach($apis as $apiClass) {
    $r->addAPIClass($apiClass);
}

but i think the whole project appreciate to use nette/di i can help with understanding of functions

[Arul-]

With the above commit that will soon be part of RC6 all you need is

Scope::$resolver = function ($className) use ($context) {
    return $context->getByType($className);
};

[Arul-]

@matak did you try the above solution?

[matak]

didnt have so much time, but this settings of composer "restler/framework": "@rc",

still doesnt work

Access to undeclared static property: Luracast\Restler\Scope::$resolver

?

[soda-2005]

With the above commit that will soon be part of RC6 all you need is
Scope::$resolver = function ($className) use ($context) {
return $context->getByType($className);
};

I tried to use the dependency-Injection (of my MVC-framework), but it did not work in Explorer (when i want to see the online-documentation for my API's). When i call the online-documentation of my API's, than this PHP-Fatal-Error appears:
PHP Fatal error: Call to a member function getRequestedApiVersion() on a non-object in Luracast/Restler/Explorer.php on line 167

The problem/bug is in class 'Scope' in Method 'get':
When Scope::$resolver is defined, than the 'logic' does not take place, where some object-properties were set. This PHP-code will not be called:
Scope:get:

       if (class_exists($fullName)) {
           $shortName = Util::getShortName($name);
           $r = new $fullName();
           static::$instances[$name] = (object)array('instance' => $r);
           if ($name != 'Restler') {
               $r->restler = static::get('Restler');
               $m = Util::nestedValue($r->restler, 'apiMethodInfo', 'metadata');
               if ($m) {
                   $properties = Util::nestedValue(
                       $m, 'class', $fullName,
                       CommentParser::$embeddedDataName
                   ) ?: (Util::nestedValue(
                       $m, 'class', $shortName,
                       CommentParser::$embeddedDataName
                   ) ?: array());
               } else {
                   static::$instances[$name]->initPending = true;
               }
           }
       }

I would be very cool, when you can fix that bug, so i could really use my own dependency-Injection :-)

[soda-2005]

oh, i forgot, i use restler in version 3.0.0-RC6

[soda-2005]

I created a new Issue (#423) for that bug:
#423