AngularJS, ng-repeat on radio and $scope.watch - angularjs

Question

I'm using this example: https://jsfiddle.net/qnw8ogrk/1/ to create my radio-buttons.
I would like to be able to use $scope.watch on the radio-buttons, but I'm not able to use:
$scope.watch('selected', ...
What should I assign to .watch to be able to detect whenever a user clicks on a radio button?

Answer 1

Actual mistake was $scope.watch should be $scope.$watch Having watcher over a scope variable would not be the good idea. Instead of placing watcher over ng-model I'd suggest you to use ng-change which will only fires up when radio button ng-model value gets changed.
<label ng-repeat="option in options">
<input type="radio" ng-change="test()" ng-model="$parent.selected" ng-value="option" />{{option}}
</label>
And then don't use get rid of $parent notation for accessing outer scope of ng-repeat you could switch to use controllerAs pattern, and then change ng-controller directive to use alias of controller. Also that will change the controller implementation, bind value to this(context) instead of $scope
Markup
<div ng-controller="mainController as vm">
<label ng-repeat="option in vm.options">
<input type="radio" ng-change="vm.test()" ng-model="vm.selected" ng-value="option" />{{option}}
</label>
</div>
Controller
appModule.controller('mainController', function($scope) {
var vm = this;
vm.selected = 'red';
vm.options = ['red', 'blue', 'yellow', 'green'];
vm.test = function() {
alert('Changed');
}
});
Forked Plunkr

Answer 2

I agree with #PankajParker, but it is possible from you controller as well. You just got the syntax wrong, it is $scope.$watch, not $scope.watch
Have a look at this: https://jsfiddle.net/qnw8ogrk/32/

Answer 3

Fiddle: https://jsfiddle.net/stevenng/qnw8ogrk/33/
Markup
<div ng-app="app">
<div ng-controller="mainController">
<label ng-repeat="option in options">
<input type="radio" ng-change="picked(this)" ng-model="$parent.selected" ng-value="option"/>{{option}}
</label>
</div>
</div>
Script
var appModule = angular.module('app', []);
appModule.controller('mainController', function($scope) {
$scope.selected = 'red';
$scope.options = ['red', 'blue', 'yellow', 'green'];
$scope.picked = function($scope) {
alert('you picked: ' + $scope.selected);
}
});