Interfaces

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?

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

Code:

---

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

---

and you then have the following classes implement it:

Code:

---

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:

Code:

---

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:

Code:

---

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

---

Thank you sunburnt..

Excellent example, just what I needed....

:D

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

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.