AngularJS: ng-if not working in combination with ng-click?

Question

Given this test case using AngularJS 1.2 rc3: http://plnkr.co/edit/MX6otx (repeated below)

1.

    ng-if toggle         


        

Answer 1

Since ngIf creates own scope, to make it work you can define toggle1 in one scope:

JS**

$scope.toggleMe = function(){
     $scope.toggle1 = !$scope.toggle1;
    }

HTML

<li ng-init="toggle1 = true">
        ng-if toggle1: {{ toggle1 }}
        <p>
            <button ng-if="toggle1"  ng-click="toggleMe()">Turn On</button>
            <button ng-if="!toggle1"  ng-click="toggleMe()">Turn Off</button>
            does not work
    </li>

See Demo Plunker

Answer 2

1. Why does 1 not work?
ng-if creates a new scope. which causes the "weird" binding behavior as explained in this video: http://egghead.io/lessons/angularjs-the-dot

2. Should 1 work?
Reading properties from the parent scope works (prototype chain), but writing to the scope creates a new property on the child scope. Creating a disconnected

3. Why does 2 work?
The same property is read from the parent scope (obj). The write in ng-click changes the "obj" object, not the scope.

4/5. Should 2 work? Can I rely 2 to work in future updates of AngularJS?
YES, this is the documented expected behavior.

Tip: I use the Chrome extension AngularJS Batarang to gain insights about which variables are on which scope.

Answer 3

1. Why does 1 not work?: Because an ngIf defines its own scope, which prototypically inherits from its parent scope (just like ngRepeat). So, when you change the value of a field inside an ngIf, you change it in the ngIf scope, and not in its parent scope.
2. Should 1 work?: No
3. Why does 2 work?: Because in that case you modify the content of an object which is referenced by the ngId scope, through inheritance.
4. Should 2 work?: Yes
5. Can I rely 2 to work in future updates of AngularJS?: Why shouldn't you?

This scope inheritance mechanism is explained very well in https://github.com/angular/angular.js/wiki/Understanding-Scopes