C#

class Animal
{
   protected void Foo(){}
}

class Cow : Animal
{
   public vod Moo(){}
}

class Farm
{
   public void Pet(Animal animal){}
}

class Farm
{
    public void Pet(Cow chicken){}
}

 class Farm
{
    public void Pet(Animal man){}
}

sundeepan wrote:

Cow chicken

sundeepan wrote:

Animal man

sundeepan wrote:

why should one not pass an object of a base class

class Program
{
    static void MakeAnimalSpeak(Animal animal)
    {
        
        animal.MakeNoise();
    }

    static void MakeAnimalSpeakCoupled(Cow animal)
    {
        // This is more tighltly coupled to cow: 
        // this method cannot be called for duck
        animal.MakeNoise();
    }


    static void Milk(Cow animal)
    {
        animal.Milk();
        animal.MakeNoise(); // Cow is mooing with happiness
    }



    static void Main(string[] args)
    {
        Cow cow = new Cow();
        Duck duck = new Duck();
        MakeAnimalSpeak(cow);
        MakeAnimalSpeak(duck);
        MakeAnimalSpeakCoupled(cow);
        //MakeAnimalSpeakCoupled(duck); //Coupled to cow: this is a worse implementation in this context
        Milk(cow);
        //Milk(duck); //Can't, but not a problem. Milking a duck is nonsensical!
    }
}



abstract class Animal
{   
    public abstract void MakeNoise();  
}

class Cow : Animal
{
    public override void MakeNoise() { Console.WriteLine("Moo"); }
    public void Milk() { Console.Write("Sloooosh"); }
}

class Duck : Animal
{
    public override void MakeNoise() { Console.WriteLine("Quack"); }    
}

Pathachiever wrote:

It only runs on Windows 7, because of the Windows 7-specific features.