Ember.js observer is triggered on initialisation also

Question

I've some troubles with the observer. I would like to observe some model properties but somehow the observer is triggered on initialisation also. I only want to trigger the function when a user is really changing one of those properties.

The observer looks something like this:

  watchProperties: function(){
    console.log('Changed :D');
  }.observes('model.propertyOne', 'model.propertyTwo', 'model.propertyThree')

The modelhook is set in another route with modelFor and the model is serialised embedded JSON data. Is it possible that one of these things causes the issue?

score 0 · Answer 1 · edited May 23 '17 at 11:57

0

This is expected behaviour (http://emberjs.com/api/classes/Ember.Object.html#method_addObserver). If you wish to trigger the function only when a property really changes, then you have two options:

Keeping track of the previous value using beforeObserver (How can an observer find out the before and after values of the observed property in Ember.js?)
Using ember-computed-change-gate (https://github.com/GavinJoyce/ember-computed-change-gate). This isn't ideal either cause you would need to create a duplicate of each property using the changeGate function (see second code example)

edited May 23 '17 at 11:57

Community

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answered Nov 11 '14 at 18:53

Thomas Brus

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Thanks Thomas. Indeed both options aren't ideal. I think in my case it's easier to observe when the inputs of the properties change. But still, there should be a specific Ember function to deal with this. – Alvin Vogelzang Nov 11 '14 at 22:14
I agree ;) By the way, you might even be able to get away with `model.changedAttributes()` to check which properties are changed & not yet persisted – Thomas Brus Nov 11 '14 at 23:18
Hmm I found another way to only observe changes after initialization. I used the addObserver method to set the observer in the next runloop. `init: function(){ this._super(); var self = this; Ember.run.later(function(){ self.addObserver('model.propertyOne', self.watchProperties); self.addObserver('model.propertyOne', self.watchProperties); self.addObserver('model.propertyOne', self.watchProperties); }); }, watchProperties: function(){ this.set('propertiesDidChange', true); },` – Alvin Vogelzang Nov 12 '14 at 10:14

Ember.js observer is triggered on initialisation also

1 Answers1