lancejpollard/index.md

## index.md

      
    Raw
  

              index.md
            
          
    Some random notes on the pangs of ember.  Will be expanding as they are uncovered.
Building a form

Say you have a form that maps to a model, something like:
<form>
  <fieldset>
    <legend>Who are you?</legend>
    <ol>
      <li class='field string required validate'>
        <label>First Name</label>
        <input name='user[first_name]'/>
      </li>
      <li class='field string required validate'>
        <label>Last Name</label>
        <input name='user[last_name]'/>
      </li>
      <li class='field string required validate'>
        <label>Email</label>
        <input name='user[email]'/>
      </li>
    </ol>
  </fieldset>
</form>
To handle this in jQuery all you have to do is this:
$(function() {
  $('#user-form').submit(function() {
    var form  = $(this);
    var data  = {};
    var id    = form.attr('id');
    var user  = App.User.find(id);
    
    $('.field', this).each(function() {
      // really, some `serialize()` function...
      var name    = $(this).attr('name');
      var value   = $(this).val();
      data[name]  = value;
    });
    
    user.updateAttributes(data);
    
    if (!user.valid()) {
      for (var key in user.errors) {
        // firstName-input (pretend at least)
        $('#' + key + '-input', form).addClass('invalid')
          .append("<output class='error'>" + user.errors[key].join("\n") + "</output>");
      }
      return false;
    }
  });
});
... it took me like 5 minutes to write that, and I'm sure I can refactor that to something reusable in any app in an hour or two.  Maybe even make it a plugin on Github, another 1 or 2 hours...
Now to make that same thing in Ember...

Build the HTML form using Handlebars markup.
Build the views
Build the controllers

Not only that, think about orders of magnitude more variables.
First, build the HTML, simple enough (and getting excited because of how simple it seems):
{{#with App.newUser}}
  <form>
    <fieldset>
      <legend>Who are you?</legend>
      <ol>
        <li class='field string required validate'>
          <label>First Name</label>
          {{view Ember.TextField valueBinding="first_name"}}
        </li>
        <li class='field string required validate'>
          <label>Last Name</label>
          {{view Ember.TextField valueBinding="last_name"}}
        </li>
        <li class='field string required validate'>
          <label>Email</label>
          {{view Ember.TextField valueBinding="email"}}
        </li>
      </ol>
    </fieldset>
  </form>
{{/with}}
Now, I don't want the model to update every time I enter something in the keyboard.  After reading through docs and source code for a few minutes, I realize I can just change
{{view Ember.TextField valueBinding="email"}}
to
<input type='text' {{bindAttr value="email"}} />
But now in the first case, I'm using an Ember.View object, and in the second case, am I using an Ember.View instance?  Not clear, so look it up in the docs.  Oh, and if I remove that <input...> element, what's going to happen do the bindings?  Now all of a sudden I can't do the quick-and-easy $('input').remove().  Instead, I have to do Ember.View.VIEWS[$('input[name="email"]').attr('id')]].destroy().  That's pretty ugly.  There's a way around that though, no worries!  All you have to do is make the <form> an Ember.View, or wrap it all in an Ember.View as a template.
But now, I want to start adding something like an autocomplete box, or the stackoverflow-like tag box.  In jQuery I can just listen to the keyup event, run some ajax, and position some divs over the text field:
$('input').keyup(function() {
  var input     = $(this);
  var position  = input.offset();
  $.ajax({
    url: '/autocomplete',
    data: {query: $(this).val()},
    success: function(words) {
      var divs = [];
      for (var i = 0; i < words.length; i++) {
        divs.push('<div>' + words[i] + '</div>');
      };
      $('#popup').empty().append(divs.join('\n'));
    }
  });
});
Again, took 2-3 minutes to whip together that function.
For Ember what do I have to do?  I have to create an App.AutocompleteView, and should that be an Ember.ContainerView or Ember.CollectionView?  Then I have to think about how and where the event handlers go (for clicking on the tag in the autocomplete box, for example).
Anyway, all of a sudden, with Ember, I have to have a full-on set of UIComponents, with very rich event handling systems, like flamejs:

alert_panel.js
button_view.js
checkbox_view.js
collection_view.js
disclosure_view.js
form_view.js
horizontal_split_view.js
image_view.js
label_view.js
list_item_view.js
list_view.js
list_view_drag_helper.js
loading_indicator_view.js
menu_view.js
panel.js
popover.js
progress_view.js
radio_button_view.js
root_view.js
scroll_view.js
search_text_field_view.js
select_button_view.js
stack_item_view.js
stack_view.js
tab_view.js
table_data_view.js
table_view.js
text_area_view.js
text_field_view.js
tree_item_view.js
tree_view.js
vertical_split_view.js

And those aren't easy classes to make, they're pretty involved.  And now I'm up to 300KB of JavaScript just to get back to the ability to do basic things I could do in a few lines of jQuery.
Anyway, I'm not going to spend the time describing the details of all this, it would take hours/days.  All I'm going to say now is I feel like I have to build basically sproutcore and then some on top of Ember.js in order to get back to what I could do with jQuery 5 minutes with only a few lines of code.