I have been going through this post regarding newly added features in EmberJS. One of them being Ember.Instrumentation, can anyone explain where do we use it, if possible with an example...Thanks

I have been going through this post regarding newly added features in EmberJS. One of them being Ember.Instrumentation, can anyone explain where do we use it, if possible with an example...Thanks

• javascript
• ember.js

Share Improve this question Follow asked Oct 16, 2012 at 17:49 Mudassir AliMudassir Ali 8,04144 gold badges3333 silver badges6060 bronze badges

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Why

Instrumentation in general is a way to measure performance and other metrics in your app by subscribing to namespaced listeners. It can also be useful for debugging.

Example

I can't take credit for making this fiddle, I only saw it last night at the NYC ember.js meetup, but this should provide some context:

http://jsfiddle/2Pn3f/6/

In my attempt to figure out who presented this, I could only find his meetup profile: http://www.meetup./EmberJS-NYC/members/6706336/

To see the magic happen, open your console and start marking students as 'here.'

See the StudentView near the top and Em.Subscribe at the bottom.

// In a view
Em.instrument("student.here", this.get('content'), function() {
    //mark student as in attendance
    this.set('inAttendance', !this.get('inAttendance'));
  }, this);
},

...

Em.subscribe('*', {
  ts: null,
  before: function(name, timestamp, payload) {
    ts = timestamp;
    //console.log('    before: ', name, JSON.stringify(payload));
    //return 'HelloFromThePast';
  },
  after: function(name, timestamp, payload, beforeRet) {
    //log metrics
    //record analytics
    //profile app
    console.log('instrument: ', name, JSON.stringify(payload), beforeRet, timestamp - ts);
  }
});

Side note

What's even cooler is that you can subscribe to ember's use of instrumentation by using the wildcard.

http://jsfiddle/dmazza/sUvdg/

Documentation

See the documentation for details: http://emberjs./api/classes/Ember.Instrumentation.html