path: root/computer/what-have-the-eventemitter-framework-ever-done-for-us.rst

What have the EventEmitter framework ever done for us?
######################################################

:date: 2011-08-31T14:08:10
:category: computer
:tags: jetpack, firefox, bugTriage

So, I was one of the people behind `the bug request`_ which lead to `the
EventEmitter framework`_.

So, when I have now a moment I was looking at my scripts how to make to
use it. The situation before was that I had this ``pageMod`` creator::

   pageMod.PageMod({
       include : interestingURLsArray,
       contentScriptWhen : 'ready',
       contentScriptFile : contentScriptLibraries,
       onAttach : function onAttach(worker, msg) {
         worker.on('message', function(msg) {
           messageHandler(worker, msg);
         });
     });

and ``messageHandler`` handler was just one very ugly
``switch(msg.cmd)`` which contained sections like::

     case "GetURL":
       libbz.getURL(msg.data.url,
           function(stuff) {
             worker.postMessage(new Message(msg.data.backMessage,
                 stuff));
           });
       break;

Not nice but useable. All the ugly switching logic was hidden behind the
corner and it was obvious what it does. Now with the advent of
``EventEmitter`` framework I should change my pageMod’s ``onAttach``
handler to contain endless list of very ugly spaghetti calls like::

        worker.port.on('GetURL', function (command) {
           libbz.getURL(command.url,
             function(stuff) {
               worker.port.emit(command.backMessage,
                   stuff);
             });
         });

What is the advantage? `What have the EventEmitter framework ever done
for us?`_ I am not sure I know what is the answer,

I guess we could improve the situation a bit if page.PageMod creator was
actually returning an instance variable and event handlers could be
hooked on it (in the similar pattern as the ``Widget``\ ’s on the
instance variable. Why it isn't possible to do so with PageMod?

.. _`the bug request`:
    https://bugzilla.mozilla.org/show_bug.cgi?id=635748
.. _`the EventEmitter framework`:
    https://addons.mozilla.org/en-US/developers/docs/sdk/latest/packages/api-utils/docs/events.html
.. _`What have the EventEmitter framework ever done for us?`:
    https://youtu.be/Qc7HmhrgTuQ