Design Patterns

Adapter.cs

var hole = new RoundHole(5);
var rPeg = new RoundPeg(5);
hole.Fits(rPeg).Dump(); // True

var sm_sqpeg = new SquarePeg(5);
var lg_sqpeg = new SquarePeg(10);
//hole.Fits(sm_sqpeg); // Error: won't compile (incompatible types)

var sm_sqpeg_adapter = new SquarePegAdapter(sm_sqpeg);
var lg_sqpeg_adapter = new SquarePegAdapter(lg_sqpeg);
hole.Fits(sm_sqpeg_adapter).Dump(); // True
hole.Fits(lg_sqpeg_adapter).Dump(); // False


class RoundHole
{
	public double Radius { get; private set; }
	
	public RoundHole(double radius)
	{
		Radius = radius;
	}
	
	public bool Fits(RoundPeg peg)
	{
		return Radius >= peg.Radius;
	}
}

class RoundPeg
{
	public double Radius { get; private set; }
	
	public RoundPeg(double radius)
	{
		Radius = radius;
	}
}

class SquarePeg
{
	public double Width { get; private set; }
	
	public SquarePeg(double width)
	{
		Width = width;
	}
}

class SquarePegAdapter : RoundPeg
{
	private readonly SquarePeg Peg;
	
	public SquarePegAdapter(SquarePeg peg) : base(peg.Width * Math.Sqrt(2) / 2)
	{
		Peg = peg;
	}
	
	public new double Radius => Peg.Width * Math.Sqrt(2) / 2;
}