How to have gsub handle multiple patterns and replacements - ruby-on-rails

Question

A while ago I created a function in PHP to "twitterize" the text of tweets pulled via Twitter's API.
Here's what it looked like:
function twitterize($tweet){
$patterns = array ( "/((([A-Za-z]{3,9}:(?:\/\/)?)(?:[-;:&=\+\$,\w]+#)?[A-Za-z0-9.-]+|(?:www.|[-;:&=\+\$,\w]+#)[A-Za-z0-9.-]+)((?:\/[\+~%\/.\w-_]*)?\??(?:[-\+=&;%#.\w_]*)#?(?:[\w]*))?)/",
"/(?<=^|(?<=[^a-zA-Z0-9-\.]))#([A-Za-z_]+[A-Za-z0-9_]+)/",
"/(?<=^|(?<=[^a-zA-Z0-9-\.]))#([A-Za-z_]+[A-Za-z0-9_]+)/");
$replacements = array ("<a href='\\0' target='_blank'>\\0</a>", "<a href='http://twitter.com/\\1' target='_blank'>\\0</a>", "<a href='http://twitter.com/search?q=\\1&src=hash' target='_blank'>\\0</a>");
return preg_replace($patterns, $replacements, $tweet);
}
Now I'm a little stuck with Ruby's gsub, I tried:
def twitterize(text)
patterns = ["/((([A-Za-z]{3,9}:(?:\/\/)?)(?:[-;:&=\+\$,\w]+#)?[A-Za-z0-9.-]+|(?:www.|[-;:&=\+\$,\w]+#)[A-Za-z0-9.-]+)((?:\/[\+~%\/.\w-_]*)?\??(?:[-\+=&;%#.\w_]*)#?(?:[\w]*))?)/", "/(?<=^|(?<=[^a-zA-Z0-9-\.]))#([A-Za-z_]+[A-Za-z0-9_]+)/", "/(?<=^|(?<=[^a-zA-Z0-9-\.]))#([A-Za-z_]+[A-Za-z0-9_]+)/"]
replacements = ["<a href='\\0' target='_blank'>\\0</a>",
"<a href='http://twitter.com/\\1' target='_blank'>\\0</a>",
"<a href='http://twitter.com/search?q=\\1&src=hash' target='_blank'>\\0</a>"]
return text.gsub(patterns, replacements)
end
Which obviously didn't work and returned an error:
No implicit conversion of Array into String
And after looking at the Ruby documentation for gsub and exploring a few of the examples they were providing, I still couldn't find a solution to my problem: How can I have gsub handle multiple patterns and multiple replacements at once?

Answer 1

Well, as you can read from the docs, gsub does not handle multiple patterns and replacements at once. That's what causing your error, quite explicit otherwise (you can read that as "give me a String, not an Array!!1").
You can write that like this:
def twitterize(text)
patterns = [/((([A-Za-z]{3,9}:(?:\/\/)?)(?:[-;:&=\+\$,\w]+#)?[A-Za-z0-9.-]+|(?:www.|[-;:&=\+\$,\w]+#)[A-Za-z0-9.-]+)((?:\/[\+~%\/.\w-_]*)?\??(?:[-\+=&;%#.\w_]*)#?(?:[\w]*))?)/, /(?<=^|(?<=[^a-zA-Z0-9-\.]))#([A-Za-z_]+[A-Za-z0-9_]+)/, /(?<=^|(?<=[^a-zA-Z0-9-\.]))#([A-Za-z_]+[A-Za-z0-9_]+)/]
replacements = ["<a href='\\0' target='_blank'>\\0</a>",
"<a href='http://twitter.com/\\1' target='_blank'>\\0</a>",
"<a href='http://twitter.com/search?q=\\1&src=hash' target='_blank'>\\0</a>"]
patterns.each_with_index do |pattern, i|
text.gsub!(pattern, replacements[i])
end
text
end
This can be refactored into more elegant rubyish code, but I think it'll do the job.

Answer 2

The error was because you tried to use an array of replacements in the place of a string in the gsub function. Its syntax is:
text.gsub(matching_pattern,replacement_text)
You need to do something like this:
replaced_text = text.gsub(pattern1, replacement1)
replaced_text = replaced_text.gsub(pattern2, replacement2)
and so on, where the pattern 1 is one of your matching patterns and replacement is the replacement text you would like.