Lære Utfordring: Polymorfisme

Programmet nedenfor inneholder en superklasse kalt Shape og tre avledede klasser kalt Rectangle, Square og Circle. Problemet med koden er at metodene ikke er riktig overskrevet, siden utdataene viser 0.0 for alle de tre Console.WriteLine-setningene, noe som innebærer at metodene til basisklassen blir kjørt i stedet for metodene til de avledede klassene.

Rediger koden slik at de to metodene, nemlig getArea og calculatePerimeter, blir korrekt overskrevet.

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());
        }
    }
}

Bruk virtual-nøkkelordet i basisklassen for å gjøre metodene overstyrbare.
I hver avledet klasse, legg til override-nøkkelordet i metode-definisjonene.

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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Rediger koden slik at de to metodene, nemlig getArea og calculatePerimeter, blir korrekt overskrevet.

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());
        }
    }
}

Bruk virtual-nøkkelordet i basisklassen for å gjøre metodene overstyrbare.
I hver avledet klasse, legg til override-nøkkelordet i metode-definisjonene.

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());
        }
    }
}

Alt var klart?

Takk for tilbakemeldingene dine!

Seksjon 5. Kapittel 5