04 Dec 2009

In case you really have to Append one array to another

Here is another problem i’ve seen people solve once too many: Append one array to another. STOP. Revisit the problem. Can’t you simply use List and move on to solving actual business problems? In case you really can’t get rid of the arrays read the following

Given()
{
	source = new[] { SourceElement };
	destination = new[] { DestinationElement };
}

and

When()
{
	source.AppendTo(ref destination);
}

and

ThenTheDestinationShouldStillHaveTheDestinationElement()
{
	Assert.AreEqual(DestinationElement, destination[0]);
}

and

ThenTheDestinationShouldHaveBeenExtendedWithTheSourceElement()
{
	Assert.AreEqual(SourceElement, destination[1]);
}

And here is the code which satisfies the requirements

public static class Extensions
{
	public static void AppendTo<t>(this T[] sourceArray, ref T[] destinationArray)
	{
		var sourceLength = sourceArray.Length;
		var destinationLength = destinationArray.Length;
		var extendedLength = destinationLength + sourceLength;
		Array.Resize(ref destinationArray, extendedLength);
		Array.Copy(sourceArray, 0, destinationArray, destinationLength, sourceLength);
	}
}

Perhaps it’s time to start (or does it exist already, cause i can’t find it) an open-source project with extension methods.

Tim Van Wassenhove

In case you really have to Append one array to another