angularJS access object property in function not working

I have a function in my controller that checks for the day, and then depending on what time it is, switches the isOpen property of my object to either true or false. I pulled in the object like this

$http.get('js/data.json').success(function(data) {
  $scope.locations = data;
});

Here is where I'm trying to change it. (i'll omit the variables I set up to save space)

$scope.checkStatus = function($scope) {


switch(day) {
        case 0: $scope.locations[0].isOpen = false;
                break;
        case 1: 
        case 2: 
        case 3: 
        case 4: 
        case 5: if( time >= $730am && time < $9pm ) {
                    $scope.locations[0].isOpen = true;
                } else {
                    $scope.locations[0].isOpen = false;
                };
                break;
        case 6: if( time >= $11am && time < $9pm ) {
                    $scope.locations[0].isOpen = true;
                } else {
                    $scope.locations[0].isOpen = false;
                };
                break;
        default: alert("default");
};

switch(day) {
        case 0: $scope.locations[0].isOpen = false;
                break;
        case 1: 
        case 2: 
        case 3: 
        case 4: 
        case 5: if( time >= $8am && time < $8pm ) {
                    $scope.locations[1].isOpen = true;
                } else {
                    $scope.locations[1].isOpen = false;
                };
                break;
        case 6: if( time >= $11am && time < $10pm ) {
                    $scope.locations[1].isOpen = true;
                } else {
                    $scope.locations[1].isOpen = false;
                };
                break;
        default: alert("default");
};

};

And so on for the rest of the locations.

This gives me the error "Cannot read property 'locations' of undefined." However, when I test $scope.locations[0].isOpen inside of the $http.get success function, it correctly shows me the property.

So I have two questions really: How do I access that object inside the checkStatus function? and is this the best way do do this? Is there some easier way I haven't thought about?

Edit:

I made it work by removing the checkStatus() function and just placing the switch statements inside the $http.get success function. It now looks like this. I'm not sure if this is best practice but it seems to be functional.

myApp.controller('MyController', function MyController($scope, $window, $http) {
  $http.get('js/data.json').success(function(data) {
    $scope.locations = data;

    // variables omitted to save space


   switch(day) {
        case 0: $scope.locations[0].isOpen = false;
                break;
        case 1: 
        case 2: 
        case 3: 
        case 4: 
        case 5: if( time >= $730am && time < $9pm ) {
                    $scope.locations[0].isOpen = true;
                } else {
                    $scope.locations[0].isOpen = false;
                };
                break;
        case 6: if( time >= $11am && time < $9pm ) {
                    $scope.locations[0].isOpen = true;
                } else {
                    $scope.locations[0].isOpen = false;
                };
                break;
        default: alert("default");
    }
 });