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Editorial Team
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Asked: 2026-05-31T17:39:18+00:00

I am currently trying to build a little widget that will retrieve a list

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I am currently trying to build a little widget that will retrieve a list of artists based on a username.

The Ruby method requires a username parameter after which an API call is made that retrieves the actual array of strings.

The web page has an input field where the user can fill out his/her username. My goal is to immediately call the ruby method and display the list of artists. My problem is being able to use the actual form input as the parameter. I figured this would be relatively easy with params[:user], in the same way it’s done in a Sinatra post method. Alas, turns out it isn’t.

I tried both a JS approach and directly calling the method after :onkeyup.

Javascript:

userChanged = function() {                  
    var user = document.getElementById("username");
    if (user.value.length != 0){                
    artists = #{RFCore::get_artists(:name => params[:user]).to_json};
    art_list.innerHTML = artists
    };
};

:onkeyup

:onkeyup => "art_list.innerHTML = #{RFCore::get_artists(:name => params[:user])[0]}"

I have substituted params[:user] with all variations I could think of such as “#{user}” and user.

The errors returned are undefined method []' for params[:user] and undefined local variable or methoduser’ for “#{user}” and user.

Perhaps there is an easy solution to this; but the feeling is starting to creep up on me my approach is wrong to begin with. I am open to any other way of achieving this.

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1 Answer

  1. Editorial Team

    As far as I understood, you are generating that JavaScript dynamically. So when your Ruby code produces it, it evaluates that RFCore::get_artists expression when you are generating the JavaScript code, not when the user interacts with the web page.

    If that’s the case, I recommend:

    1. Use jQuery. It makes your life much easier.
    2. When there’s some user interaction (e.g., a key press), use Ajax to communicate with your server to get back a list of artists.

    Here is a small Sinatra application that demonstrates this approach:

    require 'sinatra'

get '/' do
  <<html
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js" type="text/javascript"></script>
<script type="text/javascript">
function userChanged()
{
  $.get('/get-artists',
        {username: $('#username').val()},
        function(data){
          $('#artists').html(data);
        });
}
</script>
User: <input id="username" type="text">
<button onclick="userChanged();">Look up</button>
<div id="artists"/>
html
end

get '/get-artists' do
  "Generate here list for user #{params[:username]}"
end

    Please notice that the above code is just an example. The HTML generated is all wrong, no template language is being used, etc.

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