can.computes with can.Map.prototype.attr() do not set up bindings

[onyxrev]

If I use can.Map.prototype.attr() in a can.compute it doesn't set up a binding like can.Map.prototype.attr("some_property") does. I often use computes to generate dynamic links and I use .attr() to serialize the data in a can.Map for use in creating the URL parameters, for example. You may not know what data will be inside the can.Map, for example, so might want to use .attr() to explode the values out when they change.

Doesn't work:

var listenToMe = new can.Map({ iChange: "fromThis" });

can.compute(function(){
    return listenToMe.attr().iChange;
});

listenToMe.attr("iChange", "toThis");

Does work:

var listenToMe = new can.Map({ iChange: "fromThis" });

can.compute(function(){
    return listenToMe.attr("iChange");
});

listenToMe.attr("iChange", "toThis");

Example of dynamic URL:

can.compute(function(){
    var routeParams = $.extend({}, listenToMe.attr(), { analytics_section_code: "report_builder", report: reportCode });
    return can.route.url(routeParams);
});

[justinbmeyer]

I actually noticed that today while reviewing can.Map's source code. _attrs doesn't call .attr() which calls can.__reading to signal live-binding.

[onyxrev]

Maybe a naive fix? I haven't been in this part of the code before but this definitely works.

[justinbmeyer]

Thanks. Anyway you could add a test? Also, can you add a check that it updates if you add a property too? You will need to tell __reading about the __keys event (you can find this happening other places).

Ah, too bad you missed the hangout today where I went over can.Map in detail :-).

[onyxrev]

Okay - will do.

[onyxrev]

It works on addition and subtraction of properties. Added __keys and test.

[justinbmeyer]

@onyxrev Thanks big time for the fix!