C++ Interfaces

WHAT ARE INTERFACES?

  • An interface is a group of related functionalities that can belong to any class. The interfaces are created using abstract class.
  • Abstract classes are used to achieve the abstraction in C++ and abstraction in C++ is a process to hide the internal details and show functionality only.
  • The class can be made abstract by declaring at least one of its functions as pure virtual function. A pure virtual function is implemented with a virtual keyword and has =0 in its declaration and this function is called as abstract function as it has no body.

LET US HAVE A LOOK AT THE SYNTAX:

virtual void function() = 0;

LET US HAVE A LOOK AT THE EXAMPLE TO UNDERSTAND THE ABSTRACT CLASS:

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#include <iostream> 
 
using namespace std; 
 
 class Fruits   
 
{   
 
    public:  
 
    virtual void color()=0;   
 
};   
 
 class Apple : Fruits   
 
{   
 
    public: 
 
     void color()   
 
    {   
 
        cout << “I am a red apple”  <<endl;   
 
    }   
 
};   
 
class Mango : Fruits   
 
{   
 
    public:  
 
     void color()   
 
    {   
 
        cout <<“I am a yellow mango” <<endl;   
 
    }   
 
};   
 
int main( ) { 
 
    Apple a; 
 
    Mango m; 
 
    a.color();   
 
    m.color();  
 
   return 0; 
 
} 
Output
I am a red apple
I am a yellow mango

RULES FOR ABSTRACT CLASS

  • We can create a pointer and reference of base abstract class which points to the instance of child class.
  • It can have constructors.
  • Any class which has pure virtual function than that class is declared as abstract class.
  • We cannot create an object of abstract class.