Assignment to scope isn't working in directive - angularjs

Question

I have a directive below that makes a change in the scope element sections.data which i later assign to update the data on UI. However, this approach works in the function change_subnav but not in the switch case (added the comments to code). Why is this happening? The code to this change is same. Will appreciate any help here. Please let me know if I need to add more information.
Plunker- https://embed.plnkr.co/wmoJcQ/
.directive('selectSubnav', function ($parse) {
return {
restrict: 'A',
link: function (scope, element, attr) {
var change_subnav = function (subnav) {
if (scope.active_tab == 'user_exercises') {
var sections = {};
sections[subnav] = scope[scope.active_tab][subnav];
// this works
scope.$apply(function () {
$parse('sections.data').assign(scope.$parent, sections);
});
} else {
}
};
$(element).on('click', function () {
$(element).parent().children().removeClass('active');
$(element).addClass('active');
switch (attr.selectSubnav) {
case 'All':
// this doesn't work
scope.$apply(function () {
$parse('sections.data').assign(scope.$parent, scope[scope.active_tab]);
console.log(scope.sections.data);
});
break;
default:
change_subnav(attr.selectSubnav);
break;
}
});
}
}
})
UPDATE
.directive('selectSubnav', function ($parse) {
return {
restrict: 'A',
link: function (scope, element, attr) {
var currentScope = scope;
var change_subnav = function (subnav) {
if (scope.active_tab == 'user_exercises') {
var sections = {};
sections[subnav] = scope[scope.active_tab][subnav];
} else {
}
return sections;
};
$(element).on('click', function () {
$(element).parent().children().removeClass('active');
$(element).addClass('active');
var sections;
switch (attr.selectSubnav) {
case 'All':
// this doesn't work
sections = currentScope[currentScope.active_tab];
break;
default:
sections = change_subnav(attr.selectSubnav);
break;
}
currentScope.$apply(function () {
$parse('sections.data').assign(currentScope.$parent, sections);
});
});
}
}
})

Answer 1

You already have access to scope in your link function, so instead of updating scope.sections.data like this:
$parse('sections.data').assign(scope.$parent, sections);
You can simply do this:
$parse('sections.data').assign(scope, sections);
Or, better yet just update it directly, like this:
scope.sections.data = sections;