Apprendre Défi : Polymorphisme | Principes de la POO

Le programme ci-dessous contient une superclasse appelée Shape et trois classes dérivées nommées Rectangle, Square et Circle. Le problème du code est que les méthodes ne sont pas correctement substituées, car la sortie affiche 0.0 pour les trois instructions Console.WriteLine, ce qui implique que les méthodes de la classe de base sont exécutées au lieu de celles des classes dérivées.

Modifiez le code de manière à ce que les deux méthodes, à savoir getArea et calculatePerimeter, soient correctement substituées.

index.cs


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using System;
using System.Collections.Generic;

class Shape
{
    // Perimeter is the length of the 'outline' of a shape
    public float perimeter;

    // Change code below this line
    public float getArea()
    {
        return 0.0f;
    }

    protected float calculatePerimeter()
    {
        return 0.0f;
    }
    // Change code above this line
}

class Rectangle : Shape
{
    float width;
    float height;

    public Rectangle(float width, float height)
    {
        this.width = width;
        this.height = height;
        this.perimeter = this.calculatePerimeter();
    }

    // Change code below this line
    public float getArea()
    {
        return width * height;
    }

    protected float calculatePerimeter()
    {
        return width * 2 + height * 2;
    }
    // Change code above this line
}

class Square : Shape
{
    float length;

    public Square(float length)
    {
        this.length = length * length;
        this.perimeter = calculatePerimeter();
    }

    // Change code below this line
    public float getArea()
    {
        return length * length;
    }

    protected float calculatePerimeter()
    {
        return 4 * length;
    }
    // Change code above this line
}

class Circle : Shape
{
    float radius;

    public Circle(float radius)
    {
        this.radius = radius;
        this.perimeter = calculatePerimeter();
    }

    // Change code below this line
    public float getArea()
    {
        return 3.14f * radius * radius;
    }

    protected float calculatePerimeter()
    {
        return 2.00f * 3.14f * radius;
    }
    // Change code above this line
}

class ConsoleApp
{
    static void Main()
    {
        List<Shape> shapes = new List<Shape>();
        shapes.Add(new Rectangle(10f, 20f));
        shapes.Add(new Square(10f));
        shapes.Add(new Circle(10f));

        foreach (Shape shape in shapes)
        {
            Console.WriteLine(shape.getArea());
        }
    }
}

Dans la classe de base, utilisez le mot-clé virtual pour rendre les méthodes substituables.
Dans chaque classe dérivée, ajoutez le mot-clé override dans les définitions des méthodes.

index.cs


              123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107
            
using System;
using System.Collections.Generic;

class Shape
{
    // Perimeter is the length of the 'outline' of a shape
    public float perimeter;

    // Change code below this line
    public virtual float getArea()
    {
        return 0.0f;
    }

    protected virtual float calculatePerimeter()
    {
        return 0.0f;
    }
    // Change code above this line
}

class Rectangle : Shape
{
    float width;
    float height;

    public Rectangle(float width, float height)
    {
        this.width = width;
        this.height = height;
        this.perimeter = this.calculatePerimeter();
    }

    // Change code below this line
    public override float getArea()
    {
        return width * height;
    }

    protected override float calculatePerimeter()
    {
        return width * 2 + height * 2;
    }
    // Change code above this line
}

class Square : Shape
{
    float length;

    public Square(float length)
    {
        this.length = length * length;
        this.perimeter = calculatePerimeter();
    }

    // Change code below this line
    public override float getArea()
    {
        return length * length;
    }

    protected override float calculatePerimeter()
    {
        return 4 * length;
    }
    // Change code above this line
}

class Circle : Shape
{
    float radius;

    public Circle(float radius)
    {
        this.radius = radius;
        this.perimeter = calculatePerimeter();
    }

    // Change code below this line
    public override float getArea()
    {
        return 3.14f * radius * radius;
    }

    protected override float calculatePerimeter()
    {
        return 2.00f * 3.14f * radius;
    }
    // Change code above this line
}

class ConsoleApp
{
    static void Main()
    {
        List<Shape> shapes = new List<Shape>();
        shapes.Add(new Rectangle(10f, 20f));
        shapes.Add(new Square(10f));
        shapes.Add(new Circle(10f));

        foreach (Shape shape in shapes)
        {
            Console.WriteLine(shape.getArea());
        }
    }
}

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Section 5. Chapitre 5

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Modifiez le code de manière à ce que les deux méthodes, à savoir getArea et calculatePerimeter, soient correctement substituées.

index.cs


              123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107
            
using System;
using System.Collections.Generic;

class Shape
{
    // Perimeter is the length of the 'outline' of a shape
    public float perimeter;

    // Change code below this line
    public float getArea()
    {
        return 0.0f;
    }

    protected float calculatePerimeter()
    {
        return 0.0f;
    }
    // Change code above this line
}

class Rectangle : Shape
{
    float width;
    float height;

    public Rectangle(float width, float height)
    {
        this.width = width;
        this.height = height;
        this.perimeter = this.calculatePerimeter();
    }

    // Change code below this line
    public float getArea()
    {
        return width * height;
    }

    protected float calculatePerimeter()
    {
        return width * 2 + height * 2;
    }
    // Change code above this line
}

class Square : Shape
{
    float length;

    public Square(float length)
    {
        this.length = length * length;
        this.perimeter = calculatePerimeter();
    }

    // Change code below this line
    public float getArea()
    {
        return length * length;
    }

    protected float calculatePerimeter()
    {
        return 4 * length;
    }
    // Change code above this line
}

class Circle : Shape
{
    float radius;

    public Circle(float radius)
    {
        this.radius = radius;
        this.perimeter = calculatePerimeter();
    }

    // Change code below this line
    public float getArea()
    {
        return 3.14f * radius * radius;
    }

    protected float calculatePerimeter()
    {
        return 2.00f * 3.14f * radius;
    }
    // Change code above this line
}

class ConsoleApp
{
    static void Main()
    {
        List<Shape> shapes = new List<Shape>();
        shapes.Add(new Rectangle(10f, 20f));
        shapes.Add(new Square(10f));
        shapes.Add(new Circle(10f));

        foreach (Shape shape in shapes)
        {
            Console.WriteLine(shape.getArea());
        }
    }
}

Dans la classe de base, utilisez le mot-clé virtual pour rendre les méthodes substituables.
Dans chaque classe dérivée, ajoutez le mot-clé override dans les définitions des méthodes.

index.cs


              123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107
            
using System;
using System.Collections.Generic;

class Shape
{
    // Perimeter is the length of the 'outline' of a shape
    public float perimeter;

    // Change code below this line
    public virtual float getArea()
    {
        return 0.0f;
    }

    protected virtual float calculatePerimeter()
    {
        return 0.0f;
    }
    // Change code above this line
}

class Rectangle : Shape
{
    float width;
    float height;

    public Rectangle(float width, float height)
    {
        this.width = width;
        this.height = height;
        this.perimeter = this.calculatePerimeter();
    }

    // Change code below this line
    public override float getArea()
    {
        return width * height;
    }

    protected override float calculatePerimeter()
    {
        return width * 2 + height * 2;
    }
    // Change code above this line
}

class Square : Shape
{
    float length;

    public Square(float length)
    {
        this.length = length * length;
        this.perimeter = calculatePerimeter();
    }

    // Change code below this line
    public override float getArea()
    {
        return length * length;
    }

    protected override float calculatePerimeter()
    {
        return 4 * length;
    }
    // Change code above this line
}

class Circle : Shape
{
    float radius;

    public Circle(float radius)
    {
        this.radius = radius;
        this.perimeter = calculatePerimeter();
    }

    // Change code below this line
    public override float getArea()
    {
        return 3.14f * radius * radius;
    }

    protected override float calculatePerimeter()
    {
        return 2.00f * 3.14f * radius;
    }
    // Change code above this line
}

class ConsoleApp
{
    static void Main()
    {
        List<Shape> shapes = new List<Shape>();
        shapes.Add(new Rectangle(10f, 20f));
        shapes.Add(new Square(10f));
        shapes.Add(new Circle(10f));

        foreach (Shape shape in shapes)
        {
            Console.WriteLine(shape.getArea());
        }
    }
}

Tout était clair ?

Merci pour vos commentaires !

Section 5. Chapitre 5