Rails 3 UJS driver events - ruby-on-rails

Question

According to Simone Carletti blog post, Rails 3 ajax helpers have changed a lot. We are supposed to write more javascript with rails 3 than we used to with rails 2.
I tried to figure out how to show up an ajax loading gif -while an ajax query is running- in the "rails 3 way". I came up with this kind of code, which uses javascript events sent by the Rails 3 UJS driver. This example uses prototype:
<div id="wait" style="display:none">
<img src="/images/ajax-loader.gif"> Please wait...
</div>
<div>
<%= link_to 'Get', 'finished', :id => "mylink", :remote => true %>
</div>
<%= javascript_tag do %>
Event.observe('mylink', 'ajax:before', function(event) {
$('wait').show();
});
Event.observe('mylink', 'ajax:complete', function(event) {
$('wait').hide();
});
<% end %>
This works well, but I wish it was possible to write these ajax events "triggers" with the help of the prototype and scriptaculous helpers, just like when we use link_to_function for example:
<%=
link_to_function("toggle visibility") do |page|
page.toggle "wait"
end
%>
Is there a way to do that, or are we supposed to write ajax events "triggers" in javascript directly, either prototype or jquery?
Best regards,
Philippe Lang

Answer 1

The idea of UJS is to move the javascript code out of the views into separate js files. The way you're doing it is defeating that goal. Instead, I believe you should have a js file with a "dom:loaded" or similar handler that sets up handlers for rails callbacks and other events.
Something like (using prototype):
(function () {
$(document).on('dom:loaded', function (event) {
$$('a[data-remote=true]').each(function (link) {
link.on('ajax:complete', function (request) {
// do something
});
});
});
}());
This way all javascripts are separated from the view, which is the idea of unobtrusive javascript.

Answer 2

After looking at rails source code, I came up with this solution:
def javascript_event_tag(name, event, &block)
content = "Event.observe('#{name}', '#{event}', function() {"
content = content + update_page(&block)
content = content + "});"
content_tag(:script, javascript_cdata_section(content))
end
This makes it easier to react to UJS events:
<div id="wait" style="display:none">
<img src="/images/ajax-loader.gif"> Please wait...
</div>
<%= link_to 'ajax call', 'code_on_controller', :id => "mylink", :remote => true %>
<%=
javascript_event_tag('mylink', 'ajax:before') do |page|
page.show 'wait'
end
%>
<%=
javascript_event_tag('mylink', 'ajax:complete') do |page|
page.hide 'wait'
end
%>
Instead of having to write raw prototype or jquery code, you can use rails helpers.