Laravel view compositor

The earliest version I worked with Laravel was 4.2, and I'm still a big fan. Of course, I have learned a lot over the years and encountered a lot of problems and difficulties, but I still look forward to what changes will happen next in Laravel.

One of the exciting features provided by Laravel is the view extension function. In my opinion, a very powerful view extension allows developers to accurately pass variables from the global to the template.

How to use view extension?

First you must know the two different types of view extensions, namely class-based and closure-based.

<?php 
View::composer(&#39;profile&#39;, function ($view) {
    $view->with(&#39;user&#39;, [&#39;...&#39;]);
});
// 或者
View::composer(&#39;profile&#39;, &#39;App\Http\ViewComposers\ProfileComposer&#39;);

The difference is very obvious. Closures are easy to use and do not require much effort to set up, but they will cause the service provider (Service Provider) to become increasingly bloated.

On the other hand, class-based view extensions lead you to directly isolate the design principles. Another benefit is that you can test this piece of code in isolation, and other developers can more easily maintain the existing code.

In computer science, separation of concerns (SoC) is the process of breaking down a computer program into distinct features that have as little functional overlap as possible. A point of concern is any interesting place or focus in the program. Often, focus is synonymous with features or behaviors, and SoC advancements have traditionally been achieved with the help of information hiding through modularity and encapsulation.

Understanding the parameters of the View::composer method

In this example, you can see that the View::composer method has two parameters.

<?php 
View::composer(&#39;profile&#39;, function ($view) {
    $view->with(&#39;user&#39;, [&#39;...&#39;]);
});
// 或者
View::composer(&#39;profile&#39;, &#39;App\Http\ViewComposers\ProfileComposer&#39;);

The first parameter is the name of the view you want to monitor, which can be a string or array. Meaning, if this template view is rendered, your view manager will be triggered and the variables will be passed to the view.

You can also use wildcards instead of manually selecting all templates. You can conveniently use the asterisk (*) to append data to every view, even complex templates with many subdirectories.

The usage scenario is usually the sidebar or navigation element that needs to be displayed in each view.

<?php
// 为一个视图添加合成器: ~/resources/views/profile
View::composer(&#39;profile&#39;, ...);
// 为多个视图添加: ~/resources/views/profile, ~/resources/views/profile_edit and ~/resources/views/profile_settings
View::composer([&#39;profile&#39;, &#39;profile_edit&#39;, &#39;profile_settings&#39;], ...);
// 目录通配符: all files in ~/resources/views/pages/*
View::composer([&#39;*pages.*&#39;], ...);

The second parameter can be a closure function or the class name of view composer.

Both methods receive a $view parameter. Through this parameter, you can easily use method ->with() to add variables to and from the view.

<?php 
View::composer(&#39;*&#39;, function ($view) {
    $view->with(&#39;breadcrumb&#39;, [&#39;item 1&#39;, &#39;item &#39;]);
});
// 或者 
View::composer(&#39;*&#39;, &#39;App\Http\ViewComposers\NavigationComposer&#39;);
// compose 方法也有 $view 参数 
namespace App\Http\View\Composers;
use Illuminate\View\View;
class NavigationComposer
{
    /**
     * @param  View  $view
     * @return void
     */
    public function compose(View $view)
    {
        $view->with(&#39;navigation&#39;, [
            &#39;items1&#39;, &#39;items2&#39;, &#39;item3&#39;
        ]);
    }
}

Setting up the view compositor

You probably know that Laravel uses providers for a lot of things, so you can guess what’s next? Yes, we have to register a service provider, and within the provider, use the view compositor we just learned about.

ViewComposerServiceProvider.php

<?php
namespace App\Providers;
use Illuminate\Support\Facades\View;
use Illuminate\Support\ServiceProvider;
class ViewComposerServiceProvider extends ServiceProvider
{
    public function boot()
    {
        View::composer(
            &#39;pages/*&#39;, &#39;App\Http\View\Composers\NavigationComposer&#39;
        );
    }
    /**
     * 注册服务提供者
     *
     * @return void
     */
    public function register()
    {
        // TODO: 实现 register() 方法。
    }
}

The only thing left now is to register a new service provider in ~/config/app.php.

<?php
return [
  &#39;providers&#39; => [
        // ....
        /*
         * 应用的服务提供者...
         */
        App\Providers\AppServiceProvider::class,
        App\Providers\AuthServiceProvider::class,
        App\Providers\EventServiceProvider::class,
        App\Providers\RouteServiceProvider::class,
        App\Providers\ViewComposerServiceProvider::class,
        // ....
    ],
];

That’s it, now we can test the view compositor

Test the view editor

Suppose we have a page called /detail, This page requires navigation data in the form of an array (below).

<?php
namespace App\Http\View\Composers;
use Illuminate\View\View;
class NavigationComposer
{
    /**
     * @param  View  $view
     * @return void
     */
    public function compose(View $view)
    {
        $view->with(&#39;navigation&#39;, [
            &#39;items1&#39;, &#39;items2&#39;, &#39;item3&#39;
        ]);
    }
}

We can test our view editor through the ->assertViewHas(). method. This method can detect whether the view editor is listening to the right view and pass the $navigation variable to it.

<?php
class ViewComposerTest extends TestCase
{
    /**
     * @return void
     */
    public function testDetailHasNavigationItems()
    {
        $this->get(&#39;/detail&#39;)->assertViewHas(&#39;navigation&#39;);
    }
}

Although this test seems simple, at least we can know whether the view editor works.

Conclusion

A closure-based or class-based view manager will simplify the code and make it easier for developers to use it. It's also part of Laravel, why don't we use such a powerful service.

I'm looking forward to new features in Laravel, and I hope I can show you something new.

Recommended tutorial: "Laravel Tutorial"

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