Method Overriding in Dart

Method overriding occurs in Dart when a child class tries to override the parent class's method. When a child class extends a parent class, it gets full access to the methods of the parent class and thus it overrides the methods of the parent class. It is achieved by re-defining the same method present in the parent class.

This method is helpful when you have to perform different functions for a different child class, so we can simply re-define the content by overriding it.

Important Points: 

• A method can be overridden only in the child class, not in the parent class itself.
• Both the methods defined in the child and the parent class should be the exact copy, from name to argument list, except the content present inside the method i.e. it can and can't be the same.
• A method declared final or static inside the parent class can't be overridden by the child class.
• Constructors of the parent class can't be inherited, so they can't be overridden by the child class.

Simple case of method overriding

Example :
 

// Dart Program to illustrate the
// method overriding concept
class SuperGeek {
    // Creating a method
    void show() {
        print("This is class SuperGeek.");
    }
}

class SubGeek extends SuperGeek {
    // Overriding show method
    void show() {
        print("This is class SubGeek child of SuperGeek.");
    }
}

void main() {
    // Creating objects
    //of both the classes
    SuperGeek geek1 = new SuperGeek();
    SubGeek geek2 = new SubGeek();
    
    // Calling same function
    // from both the classes
    // object to show method overriding
    geek1.show();
    geek2.show();
}

Output : 

This is class SuperGeek.
This is class SubGeek child of SuperGeek.

When there is more than one child class

Example :  
 

// Dart Program to illustrate the
// method overriding concept
class SuperGeek {
    // Creating a method
    void show() {
        print("This is class SuperGeek.");
    }
}

class SubGeek1 extends SuperGeek {
    // Overriding show method
    void show() {
        print("This is class SubGeek1 child of SuperGeek.");
    }
}

class SubGeek2 extends SuperGeek {
    // Overriding show method
    void show() {
        print("This is class SubGeek2 child of SuperGeek.");
    }
}

void main() {
    // Creating objects of both the classes
    SuperGeek geek1 = new SuperGeek();
    SubGeek1 geek2 = new SubGeek1();
    SubGeek2 geek3 = new SubGeek2();
    
    // Calling same function
    // from both the classes
    // object to show method
    // overriding
    geek1.show();
    geek2.show();
    geek3.show();
}

Output : 

This is class SuperGeek.
This is class SubGeek1 child of SuperGeek.
This is class SubGeek2 child of SuperGeek.

Conclusion

Method overriding in Dart enables child classes to modify the behavior of methods inherited from their parent classes. This feature enhances code reusability and flexibility by allowing different implementations in various child classes. However, there are specific rules governing overriding, including restrictions on final and static methods. Understanding method overriding is crucial for developing modular and maintainable object-oriented programs in Dart.