in my code i have the following for watch changes in some variables

```
$scope.$watch('ns.namespacea.watchable_value', function(newVal, oldVal){
    //...
})

$scope.$watch('ns.namespaceb.watchable_value', function(newVal, oldVal){
    //...
})

$scope.$watch('ns.namespacec.watchable_value', function(newVal, oldVal){
    //...
})

```

the previous code work fine but I have many `namespaces` with a `watchable_value` and I wanna do

```
var namespaces = ['namespacea', 'namespaceb', 'namespacec'];

for (i = 0; i < namespaces.length; i++) {
    var namespace = 'ns.' + namespaces[i] + '.watchable_value';
    console.log(namespace) //prints 'ns.namespacea.watchable_value', 'ns.namespaceb.watchable_value, ..
    $scope.$watch(namespace, function(newVal, oldVal){
        //...
    })
}

```

but the callback never is called