D 编程 - this 指针

D 中的每个对象都可以通过一个重要的指针访问自己的地址，该指针称为**this**指针。**this**指针是所有成员函数的隐式参数。因此，可以在成员函数内部使用 this 来引用调用对象。

让我们尝试下面的示例，以了解this指针的概念-

import std.stdio;

class Box { 
   public: 
      // Constructor definition 
      this(double l = 2.0, double b = 2.0, double h = 2.0) { 
         writeln("Constructor called."); 
         length = l;
         breadth = b; 
         height = h; 
      }
         
      double Volume() { 
         return length * breadth * height; 
      }

      int compare(Box box) { 
         return this.Volume() > box.Volume(); 
      }

   private: 
      double length;     // Length of a box 
      double breadth;    // Breadth of a box 
      double height;     // Height of a box 
}
  
void main() { 
   Box Box1 = new Box(3.3, 1.2, 1.5);    // Declare box1 
   Box Box2 = new Box(8.5, 6.0, 2.0);    // Declare box2 
   
   if(Box1.compare(Box2)) { 
      writeln("Box2 is smaller than Box1"); 
   } else { 
      writeln("Box2 is equal to or larger than Box1"); 
   }
}

编译并执行上述代码后，它将产生以下结果-

Constructor called. 
Constructor called. 
Box2 is equal to or larger than Box1