Lazy loading your controller action

August 27, 2015

In many popular frameworks these days you can lazy load your actions in order to not invoke every action unless it is the one matched that should be dispatched.

We have multiple ways of doing so and in this article I will talk about a few different ways of doing this. I will be using Slim 3 code for examples.

Anonymous Function

This is one of the popular approaches you might take when first starting with a micro-framework like Slim. Everything is stored in the anonymous function itself for quick and dirty prototyping.

<?php
$app->get('/', function ($request, $response) use ($container) {
    $data = [
        'hello' => 'World',
        'name' => 'JohnnyFive',
        'link_url' => $container->get('helper')->makeUrl('world')
    ];

    return $response->write(
        $container->get('template')->render('mytemplate.php', $data)
    );
});

$app->get('/world', function ($request, $response) use ($container) {
    return $response->write(
        $container->get('template')->render('myothertemplate.php', ['say' => 'Hello World'])
    );
})->setName('world');

Based on the example above, we know that if the user should hit /world in the browser the only bit of code that will execute is the code within that route action. In this other example I will be using a class instead which we will assume has two methods with the code from above.

<?php
$app->get('/', function ($request, $response) use ($container) {
    return (new JohnnyFiveController($container))->hello($response);
});

$app->get('/world', function ($request, $response) use ($container) {
    return (new JohnnyFiveController($container))->say($response);
})->setName('world');

We now have a more encapsulated code, but this now feels like I am repeating myself as I would need to inject the same dependency multiple times and If this class had more methods I would have to repeat this process even more. In my opinion this is no maintainable in the long run.

Pattern based action loading

In Laravel you have the @ symbol to state your action for the defined route, while in Slim you have the : symbol. The issue I am finding with this approach is that my IDE cannot open the defining action by ctrl clicking on the string, nor can I refactor a class easily because my route actions are all defined as strings. Here is what our example above would look like in this case.

<?php
$app->get('/', 'JohnnyFiveController:hello');

$app->get('/world', 'JohnnyFiveController:say')
    ->setName('world');

This looks so much better, but you might ask where do I tell my JohnnyFiveController that $container should be passed into the __construct method, well we would have to state this elsewhere or our app would fail. We would now have to add our JohnnyFiveController into Slim’s default Di container which is Pimple. Meaning we would be defining what class the JohnnyFiveController string should be looking for in our container. To me this is tedious and time consuming and if someone was to make a mistake and reference a different class in the container pointing to the JohnnyFiveController string we would be giving wrong information. I am also growing less fond of this method because of the refactoring issues mentioned above.

A Factory for all

Recently I have started toying with the idea of adding all my controllers into a factory and then use that factory inside of the anonymous function. This means my controller are only created when needed, they are encapsulated, my IDE can refactor the class easily and my IDE can go to a method definition when I ctrl click.

<?php
$controllerFactory = new ControllerFactory($container);

$app->get('/', function ($request, $response) use ($controllerFactory) {
    return $controllerFactory->newJohnnyFiveController()->hello($response);
});

$app->get('/world', function ($request, $response) use ($controllerFactory) {
    return $controllerFactory->newJohnnyFiveController()->say($response);
})->setName('world');

I now only need to inject my dependencies once inside of my ControllerFactory and within the factory I can handle the passing around of my dependencies.

ControllerFactory code:

<?php

class ControllerFactory
{
    private $container;

    public function __construct($container)
    {
        $this->container = $container;
    }

    public function newJohnnyFiveController()
    {
        return new JohnnyFiveController(
            $this->container->get('template'), 
            $this->container->get('helper')
        );
    }
}

Using the Action out of the ADR pattern

There are cases where you might be following the ADR pattern and only have one Action Class per route. This Action Class main method would be the __invoke method. With this you can easily refactor and ctrl click the class in order to navigate to the definition if you are using PHP 5.5 class name resolution.

<?php
$app->get('/', JohnnyFiveHelloAction::class);

$app->get('/world', JohnnyFiveSayAction::class)
    ->setName('world');

The reason we are able to just call the Action Class name here is that Slim 3 will check for the __invoke method. There are resons noted on the ADR pattern website about why this is a good approach and what the benefits are.

If you have a different way of handling this and would like to share, please do so in the comments below.

I am a freelance web developer who works under the name Silent Works. I work on various open source project and try to evolve with new technologies as they arrive.

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