Lab: Interfaces#

Objective#

In this lab, we will explore the concept of interfaces. We’ll learn how to define and implement interfaces, ensuring our classes adhere to specified contracts.

Provided Code#

Carefully review the provided code. Notice how the interface IShape defines a contract without specifying implementation details. The interface declares properties and methods that implementing classes must provide.

interface IShape
{
    double Width { get; set; }
    double Height { get; set; }
    double Area { get; }
    void Scale (double factor);
}

Instructions#

Step 1: Define classes that implement IShape#

Write two classes called Rectangle and Ellipse that both implement the interface IShape.

When you’re done, you should be able to run the following code:

IShape shape1 = new Rectangle() { Width=20, Height=10 };
IShape shape2 = new Ellipse() { Width=50, Height=20 };

Console.WriteLine(shape1.Area);
Console.WriteLine(shape2.Area);

shape1.Scale(0.5);
shape2.Scale(2);

Console.WriteLine(shape1.Area);
Console.WriteLine(shape2.Area);

200

3141.5926535897934

50

12566.370614359173

Important

Note how the compile-time type (i.e. the type “on the left”) of both types is IShape.

We will create a new interface and implement it in different classes to observe interface functionality.

Step 2: Define an interface called IPositionable#

Define an interface called IPositionable that demands that its implementors define two publically gettable properties, of type int, called X and Y

Add to the Rectangle and Circle classes so that they implement the interface IPositionable.

When you’re done you should be able to run the following code:

IPositionable shape1 = new Rectangle
{
    Width = 20,
    Height = 10,
    X = 10,
    Y = 20
};

IPositionable shape2 = new Ellipse
{
    Width = 50,
    Height = 20,
    X = 5,
    Y = 2
};

Console.WriteLine($"({shape1.X}, {shape1.Y})");
Console.WriteLine($"({shape2.X}, {shape2.Y})");

(10, 20)

(5, 2)