Practice Questions on Advance dart

1. Create a generic class Pair that holds two values of any type. Implement a method to swap the values.
2. Write a mixin Logger that provides a method log(String message). Create a class Service that uses this mixin and demonstrates logging messages.
3. Implement an extension on the List class that adds a method sum() to return the sum of all numeric elements in the list.
4. Create a class User with a @deprecated annotation on a method getFullName(). Add a new method getName() and demonstrate how to use both methods.
5. Define a generic function printList<T> that takes a list of any type and prints each element. Show how to use this function with different data types.
6. Create a mixin Flyer with a method fly(). Implement a class Bird that uses this mixin and demonstrate its functionality.
7. Implement a simple annotation called @Range that takes two integers, min and max. Use this annotation on a field in a class and show how to access it using reflection.
8. Define a class Container<T> that has a method addItem(T item). Show how to use this class with different types of items.
9. Create a class Animal with a method speak(). Use a mixin Walker that adds a method walk(). Implement a class Dog that combines both and demonstrates both methods.
10. Write a program that uses an extension on the String class to add a method isNumeric() that checks if the string represents a number.

Answers and Explanations

1. Generic Class Pair

   class Pair<T, U> {
     T first;
     U second;
   
     Pair(this.first, this.second);
   
     void swap() {
       var temp = first;
       first = second;
       second = temp;
     }
   }
   

   This class holds two values of any types T and U, and provides a method to swap them.

2. Mixin Logger

   mixin Logger {
     void log(String message) {
       print('Log: $message');
     }
   }
   
   class Service with Logger {
     void performService() {
       log('Service is performed.');
     }
   }
   

   The Logger mixin provides a logging functionality that can be used in any class, such as Service.

3. Extension on List

   extension ListSum on List<num> {
     num sum() {
       return reduce((value, element) => value + element);
     }
   }
   

   This extension adds a sum() method to lists containing numeric elements, allowing you to easily calculate their sum.

4. Class User with @deprecated

   class User {
     @deprecated   String getFullName() {
       return 'John Doe';
     }
   
     String getName() {
       return 'John';
     }
   }
   

   The getFullName() method is marked as deprecated, prompting users to use getName() instead.

5. Generic Function printList<T>

   void printList<T>(List<T> list) {
     for (var item in list) {
       print(item);
     }
   }
   

   This function takes a list of any type and prints each element, demonstrating the use of generics.

6. Mixin Flyer

   mixin Flyer {
     void fly() {
       print('Flying high!');
     }
   }
   
   class Bird with Flyer {}
   

   The Flyer mixin adds flying functionality to the Bird class, which can now fly.

7. Annotation @Range

   class Range {
     final int min;
     final int max;
     const Range(this.min, this.max);
   }
   
   class Product {
     @Range(1, 100)
     int quantity;
   }
   

   This annotation marks the quantity field, and you can access it using reflection to validate the range.

8. Class Container<T>

   class Container<T> {
     List<T> items = [];
   
     void addItem(T item) {
       items.add(item);
     }
   }
   

   The Container class can hold items of any type specified when instantiated, demonstrating the use of generics.

9. Class Animal with Mixin Walker

   class Animal {
     void speak() {
       print('Animal sound');
     }
   }
   
   mixin Walker {
     void walk() {
       print('Walking');
     }
   }
   
   class Dog extends Animal with Walker {
     @override   void speak() {
       print('Woof');
     }
   }
   

   The Dog class inherits from Animal and uses the Walker mixin to provide both walking and speaking functionalities.

10. Extension on String for isNumeric()

    extension StringExtensions on String {
      bool isNumeric() {
        return double.tryParse(this) != null;
      }
    }
    

    This extension method allows any string to check if it represents a numeric value, enhancing the string class functionality.