Undefined ruby object in javascript

Question

I'm trying to do something ONLY if a variable DOES exist (the variable's name is @filter), the problem is I can't seem to figure out how to get the code to work. I keep getting

undefined method `male_filter' for nil:NilClass

even when the first if should do the trick. Here's the actual code of the javascript:

$(document).ready(function(){
    if(typeof <%=@filter%>!='undefined'){
        if(typeof <%[email protected]_filter%>!='undefined'){
            if(<%[email protected]_filter%>=='18'){
                $('#18M').addClass('active');
            }
            else if(<%[email protected]_filter%>=='21'){
                $('#21M').addClass('active');
            }
            else if(<%[email protected]_filter%>=='24'){
                $('#24M').addClass('active');
            }
        }
    }
}

I also tried adding a boolean in the controller called filterExists, and did the following:

    var filterExists=<%=@filterExists%>;
    if(filterExists==true){...}

But I still got the same error:

undefined method `male_filter' for nil:NilClass

View your page source that is generated! I do not think your serverside code is working like you think it is. Looking at the serverside code is not going to help. — epascarello
– epascarello, Commented May 31, 2013 at 17:43

the Tin Man · Accepted Answer · 2013-05-31 18:14:36Z

2

The problem is all of the ERB is interpreted on the server and then the JavaScript is served to the client where it is run, you are trying to mix server-side and client-side logic.

As long as you understand the ERB is interpreted first, then you can structure your code like this:

$(document).ready(function(){
  <% if @filter.present? %>
    <% if @filter.male_filter == '18' %>
      $('#18M').addClass('active');
    <% end %>
    <% if @filter.male_filter == '21' %>
      $('#21M').addClass('active');
    <% end %>
    <% if @filter.male_filter == '24' %>
      $('#24M').addClass('active');
    <% end %>
  <% end %>
});

Or more concisely:

$(document).ready(function(){
  <% if @filter %>
    $('#<%= @filter.male_filter %>M').addClass('active');
  <% end %>
});

edited May 31, 2013 at 18:14

the Tin Man

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answered May 31, 2013 at 17:53

Alex Peachey

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Comments

MrDanA · Accepted Answer · 2013-05-31 17:44:06Z

1

I assume this is a js.erb. You can use regular Ruby in those as well:

<% if @filter.present? %>
  <% if @filter.male_filter == "18" %>
    $('#18').addClass('active');
  <% end>
<% end %>

Etc.

answered May 31, 2013 at 17:44

MrDanA

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1 Comment

Waclock Over a year ago

I'm sorry I forgot to mention, this is a view -> html.erb.

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