Using Erik's answer, as a starting point. I found a simpler solution that worked for me.
In my ng-click function I have:
var the_string = 'lifeMeaning';
if ($scope[the_string] === undefined) {
//Valid in my application for first usage
$scope[the_string] = true;
} else {
$scope[the_string] = !$scope[the_string];
}
//$scope.$apply
I've tested it with and without $scope.$apply. Works correctly without it!