How is duck typing different from the old 'variant' type and/or interfaces?

Question

I keep seeing the phrase \"duck typing\" bandied about, and even ran across a code example or two. I am way too lazy busy to do my own research, can someone tel

Answer 1

@Kent Fredric

Your example can most certainly be done without duck typing by using explicit interfaces...uglier yes, but it's not impossible.

And personally, I find having well defined contracts in interfaces much better for enforcing quality code, than relying on duck typing...but that's just my opinion and take it with a grain of salt.

public interface ICreature { }
public interface IFly { fly();}
public interface IWalk { walk(); }
public interface IQuack { quack(); }
// ETC

// Animal Class
public class Duck : ICreature, IWalk, IFly, IQuack
{
    fly() {};
    walk() {};
    quack() {};
}

public class Rhino: ICreature, IWalk
{
    walk();
}

// In the method
List creatures = new List();
creatures.Add(new Duck());
creatures.Add(new Rhino());   

foreach (ICreature creature in creatures)
{
    if (creature is IFly)        
         (creature as IFly).fly();        
    if (creature is IWalk) 
         (creature as IWalk).walk();         
}
// Etc