how to get call back function in chat : Option 2: Explicit synchronization about angularfire

[katowulf]

@steve21124 could you describe the use case you're trying to solve? It might be there are several options available, depending on the desired result : )

[steve21124]

thanks. what I need in message transmission exactly the same as chat. Instead of sending message, it will sent lat,lon and small description.
The scenario is like this: if some one send lat,lon,description to the server the server will notify all currently connected client incoming (lat,lon,description). on the client side the javascript function will be call some function to do some update to the map.

I already have all the map stuff ready. the only things I that I need is to initial a function call when the server return a value. Currently, I put it inside "scope.$watch("messages.length", function()" but not sure if this the right approached.

[bennlich]

So it sounds like it doesn't have to happen before updating your local data--you just want to call a function whenever the data changes. Is that right?

[steve21124]

yes, whenever the data changes, it will call the function and pass that value of the changed data.

[bennlich]

Seems like this must be a pretty common use-case, and I can't think of a better way to do it than to slip an extra callback into the Firebase .on() listener. What do you think @katowulf?

[anantn]

We added an optional callback to angularFireCollection as the 2nd argument. Let us know if that doesn't suit your needs!