AngularJs: Binding ng-model to a list of radio but

Im trying to bind the selected value in a list of radio buttons to an ng-model

I have:

<!DOCTYPE html>

<html ng-app="testApp">
    <head>
        <script src="./bower_components/angular/angular.min.js"></script>
        <script src="test.js"></script>
    </head>
    <body ng-controller="testController">
        <form>
            <div ng-repeat="option in occurrenceOptions">
                <input type="radio" name="occurrence" ng-value="option" ng-model="selectedOccurrence" /><label>{{ option }}</label>
            </div>
        </form>
        <div>The selected value is : {{ selectedOccurrence }}</div>

        <!-- This works -->
        <input type="radio" ng-model="selected2" ng-value="'1'"> 1
        <input type="radio" ng-model="selected2" ng-value="'2'"> 2
        <input type="radio" ng-model="selected2" ng-value="'3'"> 3

        <div>This selected value is : {{ selected2 }} </div>
    </body>
</html>

For my controller:

(function () {

    var app = angular.module('testApp', []);

    app.controller('testController', function($scope) {
        $scope.occurrenceOptions = [];

        $scope.occurrenceOptions.push('previous');
        $scope.occurrenceOptions.push('current');
        $scope.occurrenceOptions.push('next');

        $scope.selected2;
    });
}());

In the first section, I tried to ng-repeat all the occurrenceOptions and bind them all to the same model. However, each time I select something the selectedOccurrence value does not change.

See plunkr: https://plnkr.co/edit/k1pMgkLdrMUG1blktQx1?p=preview

without the ng-repeat and just typing out all the radio buttons, I am able to get this to work. Why is the ng-repeat version not working?

The reason behind it is not working is, you are using ng-repeat & you are defining ng-model variable in it. The way ng-repeat works is, it create a new child scope(prototypically inherited) on each iteration of collection. So the ng-model which resides in ng-repeat template, belongs that newly created scope. Here ng-model="selectedOccurrence" create selectedOccurrence scope variable on each iteration of ng-repeat.

To overcome such a problem you need to follow dot rule while defining model in AngularJS

Markup

<body ng-controller="testController">
  <form>
    <div ng-repeat="option in occurrenceOptions track by $index">
      <input type="radio" name="occurrences" ng-value="option" ng-model="model.selectedOccurrence" />
      <label>{{ option }}</label>
    </div>
  </form>
  <div>The selected value is : {{ model.selectedOccurrence }}</div>
</body>

Code

$scope.model = {}; //defined a model object
$scope.model.selectedOccurrence = 'current'; //and defined property in it

Demo Plunkr

OR Another preferred way would be using controllerAs pattern while declaring controller(use this instead of $scope inside controller).

HTML

<body ng-controller="testController as vm">
    <form>
        <div ng-repeat="option in vm.occurrenceOptions">
            <input type="radio" name="occurrence" ng-value="option" ng-model="vm.selectedOccurrence" /><label>{{ option }}</label>
        </div>
    </form>
</body>

ControllerAs Demo