Question

I have the following select_tag.

<%= select_tag :days, options_for_select(["Monday", "Tuesday"]) %>  

Somewhere, in the view I defined the following variable.

<% @day_of_week = "Monday" %>

And showed it :

<%= @day_of_week %>

I would like to dynamically change @day_of week, after a value is selected from the select_tag.

Answer 1

You can use jquery for this.

Add this to the head of your html file (if you dont have jquery yet) :

<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.6.2/jquery.min.js" type="text/javascript"></script>

Wrap your text like this to give it an id :

<div id="text_to_be_changed"><%= @day_of_week %></div>

Give a specific id to your SELECT tab (if #days does not work for some reason).

<%= select_tag :days, options_for_select(["Monday", "Tuesday"]), :id => "select_days" %>  

Then add this unobtrusive JavaScript to the end of your view.
Any change to the select#days will trigger a modification of div#text_to_be_changed’s html.

<script>
$(document).ready(function(){
    $('#select_days').change(function() {
        $('#text_to_be_changed').html($(this).val());
    });
});
</script>