What are the applications of polymorphism in c plus plus?

Answer 1

Polymorphism allows an object to assume different identities and behavior at run time. However, these objects should share similar features and inherit from a basic abstract object.

For example, we have a variety of graphics objects that are capable of drawing themselves, such as Circle, Triangle, Square, Rectangle and other shapes. A basic graphics object assumes the top of the inheritance hierarchy. Derived objects are the Circle, Triangle, Square, etc. The basic object supports a method called "Draw()" that allows it to draw itself on the screen. How this method is implemented is dependent on the actual object itself. Each derived object of the basic graphics object will have its unique implementation of Draw().


C++ has a feature called "dynamic binding" that implements polymorphism. Through dynamic binding, the appropriate virtual method() of Draw() is bound to the appropriate graphics object at run time.


A real world application such as a graphics editor maintains a container of objects that the user constructs at run time. Each of these objects is required to redraw itself on the screen when the screen refreshes and updates itself. Through polymorphism, the container of objects may iterate over itself and allow each object that it contains to dynamically draw itself at run time.


Sample code at compile time:


for (i=0; objects[i]; i++)
objects[i]->draw();


At run time, objects[0] = Circle, objects[1] = Square, objects[2] = Polygon, etc.
The behavior of the program at objects[i]->draw() is undefined until run time.


Other applications that utilize the feature of polymorphism includes:

• providing to customers flight information from a variety of airlines, each airline abiding by a common set of API to access its flight information
• providing to customers pricing information of parts from a variety of brands and manufacturers
• providing to customers menu information from different restaurants in the area
• any application that requires supplying to customers a common API (user interface) to access a multitude of databases (flight information, scheduling, food vendors, pricing information, etc.)

Answer 2

The benefit of runtime polymorphism is that derived objects behave correctly even when you cannot know the exact type of the derivative in advance; all you know for certain is what kind of base class it is derived from. This ensures that even when other programmers derive new objects from the base class (which you cannopt possibly know about in advance), they will behave according to their actual type, simply by overriding the virtual methods provided by your base class. Thus you can invoke specialised methods from generic method calls, without the need for any expensive runtime type information routines (which should really only be required in debug code, if at all).