editing_settings.handlebars

<form>
  {{#if displayingErrors}}
    <div id="error_explanation" class="clearfix">
      <h5>An error stopped your settings from being saved:</h5>

      <ul>
      {{#each content.errors}}
        <li>{{ this }}</li>
      {{/each}}
      </ul>
    </div>
  <div>
  {{/if}}

  <!-- Some Ember.TextFields and stuff -->

  <button type="submit" style="float:left" class="green" {{bindAttr disabled="buttonDisabled"}}>{{#if content.isSaving}}Working...{{else}}Update Settings{{/if}}</button>
  <div class="message"></div>

</form>

settings_controller.rb

class SettingsController < ApplicationController
    
  def update
    if current_user.settings.update_attributes(params[:settings])
      render layout: nil, json: { } // Your object should go back as json
    else
      render status: 422, layout: nil, json: { errors: ['There was an unknown error updating your settings. Please contact support if the issue persists.'] } // Errors go back as 422
    end 
 end    
      
end 

settings_view.js

// The error handling for rest objects is from a ember-data pull request:
//
// https://github.com/emberjs/data/pull/228
//
// Merged in my branch as well:
//
// https://github.com/mixonic/data/tree/spinto
//
App.EditSettingsView = Ember.View.extend({
  templateName: 'ember/templates/editing_settings',
  
  buttonDisabledBinding: "content.isSaving",
  displayingErrors: false,
    
  submit: function(event) {
    event.preventDefault();
    App.store.commit();
  },
  
  setDisplayingErrors: function(){
    if (!this.getPath('content.isValid')) {
      this.set('displayingErrors', true);
    } else if (!this.getPath('content.isDirty')) {
      this.set('displayingErrors', false);
    }
  }.observes('content.isValid','content.isDirty'),

  setSuccessMessage: function(){
    if (this.getPath('content.isSaving')) {
      this.set('saving', true);
    } else if (this.get('saving')) {
      this.set('saving', false);
      this.$('.message').delay(1).html('Your settings have been saved, and the changes are live.').fadeIn(200).delay(2000).fadeOut(200);
    }
  }.observes('content.isSaving')

});