Keep your methods small and focused

I read this the other day in the middle of an article talking about design. This is one of my favorite programming idioms because it makes reuse of the methods later so much easier. I ran into an example today and it's one of those examples that when you find you can reuse one of your methods you are pleased with yourself and thank your earlier self for helping you out now.

This is a very simple example but it basically involves using a template file and copying it and renaming. Last time I was doing this I had to copy a batch of files each file with a different extension. Instead of making a method which copied the files and mentioned their extension I wrote one method that did that but which called a smaller focused method . The method in question took folder to copy from, folder to copy to, filename, newFileName and extension. The method above just called it four times with different file extensions.

Now because I have a smaller focused method I can use that method today to copy some different files. I think this is one of the key points in being able to write reusable code, small focused methods which are not heavily coupled with other classes or are trying to do more than one task. I have heard this talked about as do one thing and do it well and linked to keep it simple. To put the above rambling in a more concise manner

1. Keep your methods small and focused.

2. Your method should do one task.

If you do the two above then you will probably be keeping the code simple anyway but splitting up potentially larger methods in smaller focused methods. As a bonus these methods are then easier and quicker to test and if a bug does sneak in then because the code is split up into smaller sections any code that needs to be fixed is isolated in it's own method.