Dart Interfaces: Implicit Interface | Software Architecture

What is Interface and How to use it.

• In dart there is no keyword like interface , while in other programming language we can see that interface keyword.

• So ,in Dart, every class is implicit interface. An interface defines a syntax that a class must follow.

• There only minor change between inheritance and interface . Like if we want to use inheritance at that time we use " extend " keyword and for the interface we use " implements " .

• In interface we can not use parent class method like inheritance , so we can not use super keyword when we use implements keyword.

• we can use multiple implements in dart

• Let's understand with example .

  
    // Objectives
    // 1. Interface
  
    void main() {
  
        var tv = Television();
        tv.volumeUp();
        tv.volumeDown();
      tv.justAnotherMethod();
    }
  
    class Remote {
  
        void volumeUp() {
  
        }
  
         void volumeDown() {
  
         }
    }
  
    class AnotherClass {
  
        void justAnotherMethod(){
  
        }
  
    }
  
    // Here Remote and AnotherClass acts as Interface
    class Television implements Remote, AnotherClass {
  
        void volumeUp() {
    //        super.volumeUp();       // Not allowed to call super while implementing a class as Interface
            print("______Volume Up in Television_______");
        }
  
        void volumeDown() {
            print("______Volume Down in Television_______");
        }
  
        void justAnotherMethod() {
            print("Some code");
        }
    }
  

  

Difference Between Extends & Implements

• | extends | implements | | --- | --- | | Used to inherit a class in another class. | Used to inherit a class as an interface in another class. | | Gives complete method definition to sub-class. | Gives abstract method definition to sub-class. | | Only one class can be extended. | Multiple classes can be implemented. | | It is optional to override the methods. | Concrete class must override the methods of an interface. | | Constructors of the superclass is called before the sub-class constructor. | Constructors of the superclass is not called before the sub-class constructor. | | The super keyword is used to access the members of the superclass. | Interface members can’t be accessed using the super keyword. | | Sub-class need not to override the fields of the superclass. | Subclass must override the fields of the interface. |