What does "TypeError:can't modify frozen string" mean?

I got this error when using the Twitter gem, and passing in an array.

My code looks innocent enough - wondering what is causing this?

 def twitter_get_users(client, user_names=[])
    copy=Array.new(user_names)
    users = client.users(user_names)
  开发者_开发问答end

TypeError: can't modify frozen string
    from gems/twitter-1.0.0/lib/twitter/client/utils.rb:10:in `gsub!'
    from /gems/twitter-1.0.0/lib/twitter/client/utils.rb:10:in `clean_screen_name!'
    from /gems/twitter-1.0.0/lib/twitter/client/utils.rb:33:in `merge_users_into_options!'

Try this and see if it helps:

def twitter_get_users(client, user_names=[])
  client.users user_names.map(&:dup)
end

Ruby allows you to freeze objects so that they may not be mutated. Either the Twitter gem froze a string and then tried to call gsub! on it, or you passed in an already-frozen string.

This answer doesn't help you solve the root of your problem, but it does answer the questions of "What does this mean and why is it happening?"

1. Did you try opening up gems/twitter-1.0.0/lib/twitter/client/utils.rb and looking at line 10? :-)
2. if you can't find anything obvious in there, try grep -r '.freeze' on your rails project and on that gem's directory (gems/twitter-1.0.0/)