在D中每個對象都有通過一個名為this指針,這個指針訪問它自己的地址。this 指針是一個隱含的參數，所有的成員函數。因此，一個成員函數內，this 可以用來指調用對象。

讓我們試試下麵的例子就明白了this指針的概念：

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");
   }
}

當上麵的代碼被編譯並執行，它會產生以下結果：

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