I am trying to leverage the third parameter (extra dependencies) when registering a bound helper (Ember.Handlebars.registerBoundHelper#toc_example-with-extra-dependencies) for creating a translation helper, however I cannot seem to get it working. Here is a jsbin demo:
http://emberjs.jsbin.com/nucol/1/edit?html,js,output
Am I doing something wrong, or is this a bug?
I had a look at the source code of registerBoundHelper. It seems that when the first parameter passed to the helper is a string (which is the case in the jsbin) then the extra dependencies are ignored (method returns before). If the first parameter is not a string (like if it was referring directly to a model parameter) then the extra dependencies are added as sub-dependencies of the first parameter. I don’t really understand the reason of doing this and/or can somebody provide a working example of this extra dependencies parameter?
I’ve struggled with this too, but this is what I’ve found. The extra dependencies are the names of the properties of the first parameter which, when changed, should re-render the helper. I’ve modified your example to illustrate.
http://emberjs.jsbin.com/hihiyosu/1/edit
Basically, this is helpful when you want to pass a single object into a helper, but the helper output is dependent on multiple properties and should re-render when any of those properties changes. As you can see from my example, when you change either select, the helper output updates.