业务逻辑代码的组织

In computer software, business logic or domain logic is “the part of the program that encodes the real-world business rules that determine how data can be created, displayed, stored, and changed” (read full definition).

In Symfony applications, business logic is all the custom code you write for your app that’s not specific to the framework (e.g. routing and controllers). Domain classes, Doctrine entities and regular PHP classes that are used as services are good examples of business logic.

For most projects, you should store everything inside the AppBundle. Inside here, you can create whatever directories you want to organize things:

symfony2-project/
├─ app/
├─ src/
│  └─ AppBundle/
│     └─ Utils/
│        └─ MyClass.php
├─ vendor/
└─ web/

所有文件一定要放在Bundle里吗?

But there’s no technical reason for putting business logic inside of a bundle. If you like, you can create your own namespace inside the src/ directory and put things there:

symfony2-project/
├─ app/
├─ src/
│  ├─ Acme/
│  │   └─ Utils/
│  │      └─ MyClass.php
│  └─ AppBundle/
├─ vendor/
└─ web/

小技巧

The recommended approach of using the AppBundle/ directory is for simplicity. If you’re advanced enough to know what needs to live in a bundle and what can live outside of one, then feel free to do that.

服务的命名与定义

The blog application needs a utility that can transform a post title (e.g. “Hello World”) into a slug (e.g. “hello-world”). The slug will be used as part of the post URL.

Let’s create a new Slugger class inside src/AppBundle/Utils/ and add the following slugify() method:

// src/AppBundle/Utils/Slugger.php
namespace AppBundle\Utils;

class Slugger
{
    public function slugify($string)
    {
        return preg_replace(
            '/[^a-z0-9]/', '-', strtolower(trim(strip_tags($string)))
        );
    }
}

Next, define a new service for that class.

# app/config/services.yml
services:
    # keep your service names short
    app.slugger:
        class: AppBundle\Utils\Slugger

Traditionally, the naming convention for a service involved following the class name and location to avoid name collisions. Thus, the service would have been called app.utils.slugger. But by using short service names, your code will be easier to read and use.

最佳实践

The name of your application’s services should be as short as possible, but unique enough that you can search your project for the service if you ever need to.

Now you can use the custom slugger in any controller class, such as the AdminController:

public function createAction(Request $request)
{
    // ...

    if ($form->isSubmitted() && $form->isValid()) {
        $slug = $this->get('app.slugger')->slugify($post->getTitle());
        $post->setSlug($slug);

        // ...
    }
}

推荐的服务定义格式:YAML

In the previous section, YAML was used to define the service.

最佳实践

Use the YAML format to define your own services.

This is controversial, and in our experience, YAML and XML usage is evenly distributed among developers, with a slight preference towards YAML. Both formats have the same performance, so this is ultimately a matter of personal taste.

We recommend YAML because it’s friendly to newcomers and concise. You can of course use whatever format you like.

不必把服务的类名注册为参数

You may have noticed that the previous service definition doesn’t configure the class namespace as a parameter:

# app/config/services.yml

# service definition with class namespace as parameter
parameters:
    slugger.class: AppBundle\Utils\Slugger

services:
    app.slugger:
        class: "%slugger.class%"

This practice is cumbersome and completely unnecessary for your own services:

最佳实践

Don’t define parameters for the classes of your services.

This practice was wrongly adopted from third-party bundles. When Symfony introduced its service container, some developers used this technique to easily allow overriding services. However, overriding a service by just changing its class name is a very rare use case because, frequently, the new service has different constructor arguments.

持久层

Symfony is an HTTP framework that only cares about generating an HTTP response for each HTTP request. That’s why Symfony doesn’t provide a way to talk to a persistence layer (e.g. database, external API). You can choose whatever library or strategy you want for this.

In practice, many Symfony applications rely on the independent Doctrine project to define their model using entities and repositories. Just like with business logic, we recommend storing Doctrine entities in the AppBundle.

The three entities defined by our sample blog application are a good example:

symfony2-project/
├─ ...
└─ src/
   └─ AppBundle/
      └─ Entity/
         ├─ Comment.php
         ├─ Post.php
         └─ User.php

小技巧

If you’re more advanced, you can of course store them under your own namespace in src/.

Doctrine的映射配置

Doctrine Entities are plain PHP objects that you store in some “database”. Doctrine only knows about your entities through the mapping metadata configured for your model classes. Doctrine supports four metadata formats: YAML, XML, PHP and annotations.

最佳实践

Use annotations to define the mapping information of the Doctrine entities.

Annotations are by far the most convenient and agile way of setting up and looking for mapping information:

namespace AppBundle\Entity;

use Doctrine\ORM\Mapping as ORM;
use Doctrine\Common\Collections\ArrayCollection;

/**
 * @ORM\Entity
 */
class Post
{
    const NUM_ITEMS = 10;

    /**
     * @ORM\Id
     * @ORM\GeneratedValue
     * @ORM\Column(type="integer")
     */
    private $id;

    /**
     * @ORM\Column(type="string")
     */
    private $title;

    /**
     * @ORM\Column(type="string")
     */
    private $slug;

    /**
     * @ORM\Column(type="text")
     */
    private $content;

    /**
     * @ORM\Column(type="string")
     */
    private $authorEmail;

    /**
     * @ORM\Column(type="datetime")
     */
    private $publishedAt;

    /**
     * @ORM\OneToMany(
     *      targetEntity="Comment",
     *      mappedBy="post",
     *      orphanRemoval=true
     * )
     * @ORM\OrderBy({"publishedAt" = "ASC"})
     */
    private $comments;

    public function __construct()
    {
        $this->publishedAt = new \DateTime();
        $this->comments = new ArrayCollection();
    }

    // getters and setters ...
}

All formats have the same performance, so this is once again ultimately a matter of taste.

测试数据

As fixtures support is not enabled by default in Symfony, you should execute the following command to install the Doctrine fixtures bundle:

$ composer require "doctrine/doctrine-fixtures-bundle"

Then, enable the bundle in AppKernel.php, but only for the dev and test environments:

use Symfony\Component\HttpKernel\Kernel;

class AppKernel extends Kernel
{
    public function registerBundles()
    {
        $bundles = array(
            // ...
        );

        if (in_array($this->getEnvironment(), array('dev', 'test'))) {
            // ...
            $bundles[] = new Doctrine\Bundle\FixturesBundle\DoctrineFixturesBundle();
        }

        return $bundles;
    }

    // ...
}

We recommend creating just one fixture class for simplicity, though you’re welcome to have more if that class gets quite large.

Assuming you have at least one fixtures class and that the database access is configured properly, you can load your fixtures by executing the following command:

$ php app/console doctrine:fixtures:load

Careful, database will be purged. Do you want to continue Y/N ? Y
  > purging database
  > loading AppBundle\DataFixtures\ORM\LoadFixtures

代码规范

The Symfony source code follows the PSR-1 and PSR-2 coding standards that were defined by the PHP community. You can learn more about the Symfony Coding standards and even use the PHP-CS-Fixer, which is a command-line utility that can fix the coding standards of an entire codebase in a matter of seconds.