Introduction to __construct() and __initialize() in thinkphp

About the understanding of __construct() and _initialize() in thinkphp

There are many opinions and usages on the Internet. I tested it myself. The following is based on the test The results are combined with your own understanding to draw conclusions. If there are any mistakes, you are welcome to correct them! ! !

Let’s first take a look at the contents of the Controlle class that comes with Thinkphp (ThinkPHP\Library\Think\Controller.class.php)

Look at the constructor:

/**
     * 架构函数 取得模板对象实例
     * @access public
     */
    public function __construct() {
        Hook::listen('action_begin',$this->config);
        //实例化视图类
        $this->view     = Think::instance('Think\View');
        //控制器初始化
        if(method_exists($this,'_initialize'))
            $this->_initialize();
    }

From You can know from the constructor in the Controller class that the constructor will determine whether there is an _initialize method in the object. If so, the _initialize method will be executed first.

Therefore, if we are in the controller we define ,

1): There is an overridden constructor:

①In the rewritten construct, there is a constructor that implements the parent class (parent::construct()),

If the _initialize() method is defined in the controller, then when we call the method in the controller, we will first execute the _initialize() method, and then execute the method we need. See the code:

<?php
namespace Home\Controller;
use Think\Controller;
class IndexController extends Controller {
 
	public function __construct() {
		parent::__construct();
		self::b();
		echo &#39;我是构造<br />&#39;;
	}
	public function _initialize() {
		echo &#39;我先来<br />&#39;;
		// parent::_initialize();
	}
    public function index(){
    	self::b();
    	echo &#39;这是index&#39;;
    }
 
    public function b() {
    	echo &#39;bbbb<br />&#39;;
    }
}
 
/*
当执行index方法时，打印结果：
我先来
bbbb
我是构造
bbbb
这是index
*/

②: The constructor of the parent class is not implemented in the overridden construction. When the method is executed, the defined _initialize() method has no effect (the _initialize method will not be executed first when the method is executed) ), look at the code:

<?php
namespace Home\Controller;
use Think\Controller;
class IndexController extends Controller {
 
	public function __construct() {
		// parent::__construct();
		self::b();
		echo &#39;我是构造<br />&#39;;
	}
	public function _initialize() {
		echo &#39;我先来<br />&#39;;
		// parent::_initialize();
	}
    public function index(){
    	self::b();
    	echo &#39;这是index&#39;;
    }
 
    public function b() {
    	echo &#39;bbbb<br />&#39;;
    }
}
 
/*
当执行index方法时，打印结果：
bbbb
我是构造
bbbb
这是index
*/

Note: The _initialize() method mentioned here means that there is no function call before parent::__construct();. If you have to do it in parent:: __construct(); Comes with self::b(). It goes without saying that b() must be executed first, but it is generally not written this way. There is generally no output and configuration before the constructor of the parent class is implemented.

Furthermore, if it is inheritance, if the parent class has a constructor, the subclass generally initializes the constructor of the parent class first in its constructor to ensure the originality and integrity of the code

2) There is no overriding of the constructor, that is to say, there is no constructor declared in the controller we define

In this case, if the _initialize() method is defined in the controller, when we call other methods , the _initialize() method will be called first, look at the code:

<?php
namespace Home\Controller;
use Think\Controller;
class IndexController extends Controller {
 
	// public function __construct() {
	// 	// parent::__construct();
	// 	self::b();
	// 	echo &#39;我是构造<br />&#39;;
	// }
	public function _initialize() {
		echo &#39;我先来<br />&#39;;
		// parent::_initialize();
	}
    public function index(){
    	self::b();
    	echo &#39;这是index&#39;;
    }
 
    public function b() {
    	echo &#39;bbbb<br />&#39;;
    }
}
 
/*
当执行index方法时，打印结果：
我先来
bbbb
这是index
*/

In addition, _initialize() can also be used to inherit

<?php
namespace Home\Controller;
use Think\Controller;
class BaseController extends Controller {
	public function __construct() {
		parent::__construct();
 
		echo &#39;我是父类<br />&#39;;
	}
 
	public function _initialize() {
		echo &#39;我先来<br />&#39;;
	}
 
	public function a() {
		echo &#39;aaaa<br />&#39;;
	}
}

<?php
namespace Home\Controller;
use Think\Controller;
class IndexController extends BaseController {
 
	public function __construct() {
		parent::__construct();
		self::b();
		echo &#39;我是构造<br />&#39;;
	}
	public function _initialize() {
		parent::_initialize();
		echo &#39;我是子类先来<br />&#39;;
	}
    public function index(){
    	self::b();
    	echo &#39;这是index&#39;;
    }
 
    public function b() {
    	echo &#39;bbbb<br />&#39;;
    }
}
 
/*
当执行index方法时，打印结果：
我先来
我是子类先来
我是父类
bbbb
我是构造
bbbb
这是index
*/

Note: If there is no constructor in the parent class parent::construct(), the defined _initialize() does not work either

So, there are both __construct() (the constructor initializes the constructor of the parent class) and _initialize(), in the end Which one should be executed first?

The answer is - execute the _initialize() method first, that is to say, if the conditions are met, the _initialize() function must be executed before any method is executed, including the constructor,

Of course, if you call another or more methods in the method to be executed, when you call those methods in addition, the _initialize() method will not be executed again, it is associated with the method you called for the first time. , that is to say, it has no control over what is done in the method.

Recommended tutorial: thinkphp tutorial

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