C++ LANGUAGE CLASS MEMBER FUNCTIONS

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C++ LANGUAGE CLASS MEMBER FUNCTIONS

Class member functions 

A member function of a class is a function that has its 
definition or its prototype within the class definition 
like any other variable. It operates on any object of the 
class of which it is a member, and has access to all the 
members of a class for that object. 

Let us take previously defined class to access the members of the 
class using a member function instead of directly accessing them: 


class Box 
{ 
   public: 
      double length;         // Length of a box 
      double breadth;        // Breadth of a box 
      double height;         // Height of a box 
      double getVolume(void);// Returns box volume 
}; 


Member functions can be defined within the class definition or 
separately using scope resolution operator, ::. Defining a 
member function within the class definition declares the 
function inline, even if you do not use the inline specifier. 
So either you can 


defineVolume() function as below: 
class Box 
{ 
   public: 
      double length;      // Length of a box 
      double breadth;     // Breadth of a box 
      double height;      // Height of a box 
    
      double getVolume(void) 
      { 
         return length * breadth * height; 
      } 
}; 


If you like, you can define the same function outside the class 
using the scope resolution operator (::) as follows: 


double Box::getVolume(void) 
{ 
    return length * breadth * height; 
} 
Here, only important point is that you would have to use class 
name just before :: operator. A member function will be called 
using a dot operator (.) on a object where it will manipulate 
data related to that object only as follows: 


Box myBox;          // Create an object 
 
myBox.getVolume();  // Call member function for the object 


Let us put above concepts to set and get the value of 
different class members in a class: 


#include <iostream> 
 
using namespace std; 
 
class Box 
{ 
   public: 
      double length;         // Length of a box 
      double breadth;        // Breadth of a box 
      double height;         // Height of a box 
 
      // Member functions declaration 
      double getVolume(void); 
      void setLength( double len ); 
      void setBreadth( double bre ); 
      void setHeight( double hei ); 
}; 
 
// Member functions definitions 
double Box::getVolume(void) 
{ 
    return length * breadth * height; 
} 
 
void Box::setLength( double len ) 
{ 
    length = len; 
} 
 
void Box::setBreadth( double bre ) 
{ 
    breadth = bre; 
} 
 
void Box::setHeight( double hei ) 
{ 
    height = hei; 
} 
 
// Main function for the program 
int main( ) 
{ 
   Box Box1;                // Declare Box1 of type Box 
   Box Box2;                // Declare Box2 of type Box 
   double volume = 0.0;     // Store the volume of a box here 
  
   // box 1 specification 
   Box1.setLength(6.0);  
   Box1.setBreadth(7.0);  
   Box1.setHeight(5.0); 
 
   // box 2 specification 
   Box2.setLength(12.0);  
   Box2.setBreadth(13.0);  
   Box2.setHeight(10.0); 
 
   // volume of box 1 
   volume = Box1.getVolume(); 
   cout << "Volume of Box1 : " << volume <<endl; 
 
   // volume of box 2 
   volume = Box2.getVolume(); 
   cout << "Volume of Box2 : " << volume <<endl; 
   return 0; 
} 
When the above code is compiled and executed, it produces the following result: 
Volume of Box1 : 210 
Volume of Box2 : 1560