Interfaces

[Hinder]

It was suggested to me to use Interfaces on a project i'm working on because you are supposed to be able to Iterate through a interface regardless of the classes that use them. I'm a bit confused on exactely what that means. Does it mean that I could have 5 different classes using one interface and I would be able to Iterate through all the classes that are using that Interface?

[sunburnt]

suppose you have the interface IPhysicalObject, which implements the following members: (C#, you get the idea though)

public interface IPhysicalObject
{
     double GetWeight();
     string GetName();
     Color GetColor();
};

and you then have the following classes implement it:

public class MyBox : IPhysicalObject
{
     public double GetWeight() { return 15.00; } ;
     public String GetName() { return "My Heavy Red Chest"; };
     public Color GetColor() { return Color.Red; };
     public void Lock() { /* .... */ };
     public void Unlock() { /* .... */ };

};

public class MyFridge: IPhysicalObject
{
     public double GetWeight() { return 100.00; } ;
     public String GetName() { return "My Big Refrigerator"; };
     public Color GetColor() { return Color.White; };

     public bool IsFoodRotten() { /* .... */ };
};

public class MyShirt: IPhysicalObject
{
     public double GetWeight() { return .5; } ;
     public String GetName() { return "My Green Shirt"; };
     public Color GetColor() { return Color.Green; };

     public void TurnInsideOut() { /* .... */ };
};

now suppose you wanted to keep these three things in an array together, maybe for some weird game where you had objects in a room:

myShirt shirt = new myShirt();
myFridge fridge = new myFridge();
myBox box = new myBox();

ArrayList myRoom = new ArrayList();
myRoom.Add(shirt);
myRoom.Add(fridge);
myRoom.Add(box);

since all the objects in your array implement IPhysicalObject, you can do something like this:

foreach(IPhysicalObject myObj in myRoom)
{
    Console.Write("This Object [" + myObj.Name + "]");
    Console.WriteLine("is " + myObj.Color.ToString());
}

[Hinder]

Thank you sunburnt..

Excellent example, just what I needed....

[nswan]

is that the only real use interfaces have? For when you iterate through a collection of different object using the same one?

I never bother using interfaces to be honest as i never saw the point of them. Am beginning to from this example tho!

Nick

[Cander]

They also provide a set of rules that a class must follow that can be enforced. for example if you make your app have a plugin system. You would want to create an interface so that all plugins have a set functions and properties that they MUST write code for because those are what the main app will expect.