AngularJS - bug with ng-disabled? Not updating with new values

Question

I'm somewhat new to angular and have come across a very weird problem, I'm sure others have too.

Let's say that this is the code for my button:

<button type="submit" ng-click="submit(something)" id="coolButton" 
        ng-disabled="type === 0 || code === ''" 
        >Check-In</button>

So, basically if either type is 0 or code is nothing (no text), then this button will be disabled.

Now's here where my problem starts: If I load the page with type = 0 and code = '', then sure enough it's disabled. If, I change both of these values then of course the button will be enabled.

However, if I change the values back to 0 and '', then the button won't become disabled again. I know for a fact that the values are in fact 0 and '' as I've printed their values out on the page.

What could be causing ng-disabled to not run the expression again?

Solution

I created working plunker here for you, to check that scenario described above is working:

<div ng-controller="HomeCtrl">

    <button type="submit" 
      ng-click="submit(something)" 
      id="coolButton" 
      ng-disabled="type === 0 || code === ''" 
      >Check-In</button><br />

    <div>type: <input ng-model="type" type="number" /></div>
    <div>code: <input ng-model="code" type="text"   /></div>

    <div>is type equal zero: {{type === 0 }}</div>
    <div>is type code empty: {{code === '' }}</div>

</div>

<script type="text/javascript"> 
var app = angular
.module('MyApp', [])
.controller('HomeCtrl', ['$scope', function ($scope) { 
  $scope.something = function(sth){alert(sth)};
  $scope.type = 0;
  $scope.code = "";
}])
</script>

Important parts here are inside of the controller, where we explicitly init the code and type. Otherwise both will start with undefined/null.

Check it here

Also, I would strongly suggest to change that style of $scope.type, $scope.code. It could bring some surprising behaviour sooner or later...

We should use some kind of Model cluster, which represents some reference which could be easily passed and does have a dot (see: https://stackoverflow.com/a/21882900/1679310)

// controller
$scope.Model = {
  type : 0,
  code : '', 
}

// directive ngDisabled in the view
ng-disabled="Model.type === 0 || Model.code === ''"