指向D类的指针（Pointer to D classes）

指向D类的指针与指向结构的指针完全相同，并且访问指向使用成员访问运算符 - >运算符的类的指针的成员，就像使用指向结构的指针一样。 与所有指针一样，您必须在使用之前初始化指针。

让我们尝试以下示例来理解指向类的指针的概念 -

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; 
      } 
   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 
   Box *ptrBox;                // Declare pointer to a class.
   // Save the address of first object 
   ptrBox = &Box1; 
   // Now try to access a member using member access operator 
   writeln("Volume of Box1: ",ptrBox.Volume()); 
   // Save the address of first object 
   ptrBox = &Box2;  
   // Now try to access a member using member access operator 
   writeln("Volume of Box2: ", ptrBox.Volume()); 
} 

编译并执行上述代码时，会产生以下结果 -

Constructor called. 
Constructor called. 
Volume of Box1: 5.94 
Volume of Box2: 102