So, in response to an earlier post, “mexx” asks:

Let’s say that I have a class BigTree and I have a string ‘big_tree’ how do you get the string translated to ‘BigTree’ so that I can use this translated string the way you showed?

That’s a fun challenge. Well, as I’ll later show, it’s a problem to which I already know the answer. But I gave it a shot, and came up with this – my first genuine, off-the-top-of-my-head one-liner (and I wasn’t golfing):

def camelize(str)
  str.split('_').map {|w| w.capitalize}.join
end

That’s a bit cryptic. To decode it, if Ruby’s not your first language:

1. Take a string
2. Split it on underscore characters into an array
3. Capitalize each item in the array in turn (which I do by mapping the array to a new array, with the built-in String method capitalize)
4. …and then join the whole array back into a string

Unfortunately, that works for mexxx’s example – big_tree will map to BigTree but it’s certainly not true for all possible classnames.

But, as I said earlier, I already know the answer to this. It’s part of Rails – specifically, it’s in the Inflector component of ActiveSupport. Go to the API docs and look for “camelize”. Most of the Inflector components are dependent on each other; camelize, fortunately, is only dependent on itself. And it looks like this:

def camelize(lower_case_and_underscored_word, first_letter_in_uppercase = true)
  if first_letter_in_uppercase
    lower_case_and_underscored_word.to_s.gsub(/\/(.?)/) { "::" + $1.upcase }.gsub(/(^|_)(.)/) { $2.upcase }
  else
    lower_case_and_underscored_word.first + camelize(lower_case_and_underscored_word)[1..-1]
  end
end

That looks a whole lot more convincing and generic. And I think that’s your answer, mexxx. So don’t thank me – thank the Rails core team. There’s lots of useful basic Ruby tools hidden in the Rails sourcecode – it’s always worth an explore, if only to find out more about how it does its stuff.