How to encode / decode UTF-8 in HTTP headers in Rails?

I am using "Inserting Rails Flash Messages in HTTP Headers to Display Ajax Error Templates", for example:

Controller:

 def flash_as_header
   return unless request.xhr?
   [:error, :warning, :notice].each do |type|
    if flash[type]
     response.headers["X-Ajax-#{type.to_s.humanize}"] = flash[type]
    end
   end
 end

      

        
        
        
      

    

JQuery

 $(document).ajaxComplete(function(response, status, xhr) {
    var types = ["Error", "Notice", "Warning"];
    for (i = 0, l = types.length; i < l; ++i) {
        msg = status.getResponseHeader("X-Ajax-" + types[i]);
        if(msg) {
            break;
        }
    }
    if(msg) {
        $('.flash-error').text(msg).removeClass('is-hidden');
    }
 });

      

        
        
        
      

    

This works, but I am running into character encoding issues. Flash messages contain special characters UTF-8, and the target HTML document is UTF-8.

Here's an example of a line that should appear:

Användare

      

        
        
        
      

    

This is how it is done in the HTTP response (correct: %C3%A4

yes):

X-Ajax-Error:Anv%C3%A4ndare

      

        
        
        
      

    

And this is how it is displayed in the HTML document:

Användare

      

        
        
        
      

    

This is consistent with this table ( http://www.i18nqa.com/debug/utf8-debug.html ) which says that "the problem is caused by UTF-8 bytes, which are interpreted as Windows-1252 Byte (or ISO 8859- 1)."

I'm not sure how and where to fix this: in a JQuery function, in a Rails Controller, or in an HTML template?