Difference between abstract class and interface

Question

Difference between abstract class and interface and real world situation where you will use interface and abstract classes.

Avadhesh Tiwari · Answer

An Abstract Class can contain implementation of methods fields constructors etc while an Interface only contains method and property prototypes. An Interface defines what it can do  and an Abstract Class defines what it is. Points to use them: If you anticipate creating multiple versions of your componentcreate an abstract class. Abstract classes provide a simple and easy way to version your components. By updating the base class all inheriting classes are automatically updated with the change. Interfaces on the other hand cannot be changed once created. If a new version of an interface is required you must create a whole new interface. If the functionality you are creating will be useful across a wide range of disparate objects use an interface. Abstract classes should be used primarily for objects that are closely related whereas interfaces are best suited for providing common functionality to unrelated classes. If you are designing small concise bits of functionality use interfaces. If you are designing large functional units use an abstract class. If you want to provide common implemented functionality among all implementations of your component use an abstract class. Abstract classes allow you to partially implement your class whereas interfaces contain no implementation for any members.