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Refactoring Regular Expressions with Ruby 1.9 Named Captures

Brandon Beacher

I’ve often felt like Ruby Regexp captures are a bit clumsy.

Let’s say we need to break apart phone numbers:

After executing this match, we might do something like this with the parsed number:

What’s up with the dollar signs and the sequential numbers?

I feel like I’m writing assembly code and referring to registers or memory offsets or something.

If I’m a new Ruby programmer reading this code, I might have no idea what is going on here.

We can do better if we upgrade from magical variables to the Regexp.last_match method:

At least this is a bit more readable than the magic variables.

And it’s probably easier for a newcomer to find documentation for Regexp.last_match than $1.

But there’s an even better way in Ruby 1.9 – named captures:

Now we’ve got readable code, and better documentation built into our regular expression.

Are you using Ruby 1.9 yet? If so, have you had a chance to use named captures?

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