D 程式設計 - 指向類

指向 D 類的指標與指向結構的指標完全相同，若要訪問指向類的指標的成員，可以使用成員訪問運算子 -> 運算子，就像對指向結構的指標所做的那樣。此外，與所有指標一樣，在使用指標之前，必須初始化該指標。

讓我們嘗試以下示例來理解指向類的指標的概念 -

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()); 
} 

編譯並執行上述程式碼時，將產生以下結果 -

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