What is 'composite pattern'?

Question

Could anybody please explain and give a real-live example of Composite Design Pattern?

Answer 1

The composite pattern can be used when a collection of objects should be treated the same way as one object of the same type. This is often used with tree-structured data. Below is an example where this pattern suits well:

public abstract class Shape {
    public abstract void Draw();
}

public class Line : Shape {
    public override void Draw() {
        // Draw line
    }
}

public class Polygon : Shape {

    private IList<Line> lines;

    public override void Draw() {
        foreach (Shape line in lines) {
            line.Draw();
        }
    }
}

As you can see, the pattern makes it possible for the code dealing with drawing shapes to be unaware of how many lines are drawn.