方法链 PHP OOP

问题描述

通常，在许多框架中，您可以找到使用查询构建器创建查询的示例.你经常会看到:

Commonly, in a lot of frameworks, you can find examples of creating a query using the query builder. Often you will see:

$query->select('field');
$query->from('entity');

但是，在某些框架中你也可以这样做

However, in some frameworks you can also do it like this

$object->select('field')
       ->from('table')   
       ->where( new Object_Evaluate('x') )
       ->limit(1) 
       ->order('x', 'ASC');

您实际上是如何制作这种链条的?

How do you actually do this kinds of chains?

推荐答案

这叫做 Fluent Interface -- 该页面上有一个 PHP 示例.

This is called Fluent Interface -- there is an example in PHP on that page.

基本思想是该类的每个方法(您希望能够链接) 必须返回 $this -- 这使得调用其他方法成为可能返回的 $this 上同一个类的方法.

The basic idea is that each method (that you want to be able to chain) of the class has to return $this -- which makes possible to call other methods of that same class on the returned $this.

当然，每个方法都可以访问类的当前实例的属性——这意味着每个方法都可以向当前实例添加一些信息".

And, of course, each method has access to the properties of the current instance of the class -- which means each method can "add some information" to the current instance.

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