Rails Metal + Thin = no ‘each’ for String?

M. E. Patterson — Mon, 18 Jan 2010 04:31:17 +0000

Just solved an interesting problem when using the latest Thin web server (1.2.5) with Ruby 1.9.1 and Rails Metal.

The code in Rails Metal endpoint:

def call(env)
if env["PATH_INFO"] =~ /^\/tags.txt/
request = Rack::Request.new(env)
params = request.params
query = params['q']
[200, { "Content-Type" => "text/plain" }, words_from(query).join("\n")]
else
[404, { "Content-Type" => "text/html" }, "Not Found"]
end
end

Don’t worry about what words_from(query) actually does. It just returns an array of words. The deal is, I was trying to output a list of tags for use with a javascript autocompleter — one tag per line in a plain/text file for speed. Sure, sure, I could use JSON or XML or whatever, but I didn’t, because it was easier to get the javascript thing working quickly this way and I’m lazy.

Under ruby 1.8.7 with thin or webrick, this works fine. Under ruby 1.9.1 with Webrick (ugh!), this works fine. Under ruby 1.9.1, with Thin, this bombs with:

!! Unexpected error while processing request: undefined method `each’ for #

After two hours of debugging, here’s the simple fix — pass an array with one string element to the return line instead of a pure string object:

[200, { "Content-Type" => "text/plain" }, [words_from(query).join("\n")]]

Seriously? Yes. Seriously.

This makes Thin happy and prevents it from trying to enumerate a String, which doesn’t work in Ruby 1.9.

I haven’t gone back yet to see if this borks the other web servers, but I’m using Thin on this one anyway, so at the moment I don’t really care. As always, your mileage may vary.

M. E. Patterson - Author, Geek » thin

Rails Metal + Thin = no ‘each’ for String?