Learn to Program, 3rd Edition

Renaming Photos

Let’s do something more useful now. A while back, my wife wanted a program to download the photos from her camera’s memory card and rename them. Let’s build something like that program.

We’ll need a few more of Ruby’s built-in methods to accomplish this. The first is the Dir[] method. We’ve seen [] used with arrays before—you did know that was a method, didn’t you? Yep, it sure is. You say “arr[2]” and I say “arr.[](2)”—it’s all the same.

Anyway, rather than using an array’s [] method, we’re using the object Dir’s [] method. (Dir is for directory.) And instead of passing in a number, as with arrays, this time you pass in a string. This isn’t just any string; it’s a string describing which filenames you’re looking for. It ...