Principles of OOP

Encapsulation

Encapsulation is the process of concealing a class’s implementation details from the outside world. The public interface is the only way to interact with an object. This means that the internal state of the object is hidden from the outside world. The internal state of the object can only be changed by calling public methods. This is a very powerful concept because it allows us to change a class’s implementation without affecting the code that uses it.

Abstraction

Abstraction is the process of concealing a class’s implementation details from the outside world. The public interface is the only way to interact with an object. This means that the internal state of the object is hidden from the outside world. The internal state of the object can only be changed by calling public methods. This is a very powerful concept because it allows us to change a class’s implementation without affecting the code that uses it.

Inheritance

Inheritance is the process of creating a new class from an existing class. The new class is called a subclass, and the existing class is called a superclass. The subclass inherits all the public and protected methods from the superclass. In addition, it can have its own methods in addition to the superclass methods. Inheritance is a powerful concept because it allows us to create a new class that is based on an existing class, thus reducing the amount of code that we need to write.

Projects

1. A Game

Create a simple game that uses classes to represent different game entities, such as the player, enemies, and items.

2. Abstract Class

Create an abstract class called ArticleDataSource with method getArticle(String id), and deleteArticle(String id).
Create a class called ArticleLocalDataSource and implement the ArticleDataSource
Implement each method and print operation with the provided id. For example, calling getArticle('dart-today-and-tomorrow') should print Get dart-today-and-tomorrow
Add a factory constructor to ArticleLocalDataSource and return the object of ArticleLocalDataSource.
Instantiate ArticleLocalDataSource using the factory constructor and call each methods on the object.

3. Color Points

The class “Point” is defined as follows:

class Point {

  int _x, _y;

  Point(this._x, this._y);

  void move(int mx, int my) {

    _x += mx;

    _y += my;

  }



  void display() {

    print("x = $_x   y = $_y");

  }

}

Define a new class PointCol derived from Point to manipulate colored points.
Its constructor initializes the color of the object with a given integer (the color reference).
Add a method “printColor” that print the color.
Create a small test program (main).

4. Create a class “Client” that have 2 private attributes

Name (can’t be changed).
PurchasesAmount (double) have 2 methods (get, add).
Create a constructor that initialize the name.
Create a class “LoyalClient” that have 1 private attribute :
PurchasesAmount (double) have 1 methods (get).
Create a method “discount” that assign to PurchasesAmount (subclass) the value of PurchasesAmount (superclass) after reduction of 10%.
Create a small test program (main) .

Note : Use different names for the get methods.