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Question on book <Dive into Design Patterns>, Inheritance

Jasper Lai il y a 1 an mis à jour par Alexander Shvets il y a 1 an 1
On page 19, if a superclass implements an interface, all of its subclasses must also implement it

I don't understand it. For example, The below C# sample code I wrote, it has no compile error.
Bird "superclass, implement the Ifly"
Duck "subclass of Bird, but have not implement the Ifly"

Am I mis-understand it?



var duck = new Duck();
duck.Flying(4);

interface Ifly
{
    void Flying(int distance);
}

abstract class Bird : Ifly
{
    public void Flying(int distance)
    {
        Console.WriteLine($"I am flying {distance} miles!");
    }
}

class Duck : Bird
{}

-- Jasper

Completed

Hi!

Sorry for the confusion. I mean that all the subclasses already implement it implicitly if the superclass implements it explicitly. In other words, you can't refuse to have some parts of the original interface in a subclass, it already implements it and you can't change that.