php Trait基類use trait,本類不use

一 回顧trait使用

https://blog.csdn.net/bushuwei/article/details/103514174
發現之前本人說明很模糊，自己居然不知道為什麼
其實這裡的$c,就是class B
再次回顧邏輯

二 分析

• self和static區別說的沒毛病
• Trait基類use trait,本類不use。那麼如果用的new self，則你new 出來的就是 use trait者。如果new static，則因為有繼承關係， 它會判斷類是否存在(父子會被認為都是同一個static，則不再new)，那麼，誰先調用instance，那麼new出來的就是誰。‘Trait基類use trait,本類不use’->直接‘其實這裡的$c,就是class B’是錯的。之所以有這個‘幻覺’，是因為單例模式，且static

三 上代碼

1. self+單例
   

   trait A{
       private static $instance;
       static function getInstance()
       {
           if(!isset(self::$instance)){
               self::$instance = new self();
           }
           return self::$instance;
       }
   }
   
   class B{
       use A;
       function a()
       {
           var_dump('call at B');
       }
   }
    
   class C extends B{
       function a()
       {
           var_dump('call at c');
           parent::a();
       }
   }
    
   class D extends B{
       use A;
       function a()
       {
           var_dump('call at D');
           parent::a(); 
       }
   }
   $b = B::getInstance();
   $c = C::getInstance();
   $d = D::getInstance();
    
   $c->a();
   echo "<br/>";
   $d->a();
   echo "<br/>";
   

   　　

   string(9) "call at B"
   string(9) "call at D" string(9) "call at B" 

   註視掉

   // $b = B::getInstance();
   結果不變

2. static+單例
   

   trait A{
       private static $instance;
       static function getInstance()
       {
           if(!isset(self::$instance)){
               self::$instance = new static();
           }
           return self::$instance;
       }
   }
   
   class B{
       use A;
       function a()
       {
           var_dump('call at B');
       }
   }
    
   class C extends B{
       function a()
       {
           var_dump('call at c');
           parent::a();
       }
   }
    
   class D extends B{
       use A;
       function a()
       {
           var_dump('call at D');
           parent::a(); 
       }
   }
   $b = B::getInstance();
   $c = C::getInstance();
   $d = D::getInstance();
    
   $c->a();
   echo "<br/>";
   $d->a();
   echo "<br/>";
   

   string(9) "call at B"
   string(9) "call at D" string(9) "call at B" 
   

   　

   註視掉

   // $b = B::getInstance();

   string(9) "call at c" string(9) "call at B"
   string(9) "call at D" string(9) "call at B" 

    

3. 　self+非單例

   　　

   trait A{
       private static $instance;
       static function getInstance()
       {
           self::$instance = new self();
           return self::$instance;
       }
   }
   
   class B{
       use A;
       function a()
       {
           var_dump('call at B');
       }
   }
    
   class C extends B{
       function a()
       {
           var_dump('call at c');
           parent::a();
       }
   }
    
   class D extends B{
       use A;
       function a()
       {
           var_dump('call at D');
           parent::a(); 
       }
   }
   $b = B::getInstance();
   $c = C::getInstance();
   $d = D::getInstance();
    
   $c->a();
   echo "<br/>";
   $d->a();
   echo "<br/>";
   

   　　

   string(9) "call at B"
   string(9) "call at D" string(9) "call at B" 
   

   　　註釋掉

   // $b = B::getInstance();

   結果不變

4.  static+非單例
   

   trait A{
       private static $instance;
       static function getInstance()
       {
           // if(!isset(self::$instance)){
           //     self::$instance = new static();
           // }
           // return self::$instance;
           self::$instance = new static();
           return self::$instance;
       }
   }
   
   class B{
       use A;
       function a()
       {
           var_dump('call at B');
       }
   }
    
   class C extends B{
       function a()
       {
           var_dump('call at c');
           parent::a();
       }
   }
    
   class D extends B{
       use A;
       function a()
       {
           var_dump('call at D');
           parent::a(); 
       }
   }
   $b = B::getInstance();
   $c = C::getInstance();
   $d = D::getInstance();
    
   $c->a();
   echo "<br/>";
   $d->a();
   echo "<br/>";
   

   　　

   string(9) "call at c" string(9) "call at B"
   string(9) "call at D" string(9) "call at B" 
   

   　　註釋掉
   $b = B::getInstance();
   結果不變
   
   

四 結論

• self的話，就是誰use的，就是誰
• static的話，誰調用的就是誰
• 但是static會出現‘誰use就是誰’的幻覺，那是因為單例模式，前面創建了相同類型的單例。