Question

This is the code that I’m looking at:

def method_missing(id, *args)
    return self.find(Regexp.last_match(1),  args[0]) if id.id2name =~ /find_by_(.+)/
    raise NoMethodError
end

What happens if I have multiple threads calling Regexp.last_match?

What happens if I have multiple threads calling the object with the method_missing method?

Answer 1

The Ruby 1.9.2 platform docs state that calling Regexp.last_match is equivalent to reading the special $~ global variable.

From “The Ruby Programming Language”, pg 318: “it is important to remember that $~ and the variables derived from it are all thread-local and method-local.”

So Regexp.last_match is thread-safe. As for the other methods you are using in method_missing, I believe they are thread-safe as well. (If anybody knows differently, please edit this post.)