指向C++類

指向類的指標

指向C++類的指標與指向結構體的指標以及指向類的成員的訪問方式完全相同，您使用成員訪問運算子->運算子，就像您使用指向結構體的指標一樣。此外，與所有指標一樣，您必須在使用指標之前初始化它。

指向類的指標示例

讓我們嘗試以下示例來理解指向類的指標的概念：

#include <iostream>
 
using namespace std;

class Box {
   public:
      // Constructor definition
      Box(double l = 2.0, double b = 2.0, double h = 2.0) {
         cout <<"Constructor called." << endl;
         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
};

int main(void) {
   Box Box1(3.3, 1.2, 1.5);    // Declare box1
   Box Box2(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
   cout << "Volume of Box1: " << ptrBox->Volume() << endl;

   // Save the address of second object
   ptrBox = &Box2;

   // Now try to access a member using member access operator
   cout << "Volume of Box2: " << ptrBox->Volume() << endl;
  
   return 0;
}

當以上程式碼編譯並執行時，會產生以下結果：

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