Updating Angular view based on service parameter change

In-depth Inquiry
I have a specific setup with a header view and a main view in my Angular application. The goal is to include a "back" button in the header that should only be visible based on the current page I'm viewing.

Actions Taken
In my app.js file, I created a snippet as follows:

app.factory('globalServices', function() {
    return {
        showBack : false,
        back: function() {
            window.history.back();
        }
    };
});

For the header.html file, here's a snippet:

<a class="button-prev" ng-click="back()" ng-show="showBackButton">
    Back
</a>

In the headerCtrl.js file, I included these snippets:

$scope.showBackButton = globalServices.showBack;
$scope.back = function() {
    globalServices.back();
};

And for subPageCtrl.js, this snippet was added:

globalServices.showBack = true;

Hurdle Encountered
The visibility of the button does not update immediately after the value changes. It only reflects the change once I navigate to another page.

Is there a solution to rectify this issue?

If anyone has alternative approaches in mind, feel free to share.

Additional Note
An attempt to resolve the problem by calling $scope.$apply(); resulted in an error stating $digest already in progress, likely due to changing the value within the constructor of subPageCtrl.

Answer №1

$scope.showBackButton = globalServices.showBack;

Upon controller initialization, the value of $scope.showBackButton is set to globalServices.showBack. Any alterations made to globalServices.showBack in the future will not be reflected in $scope.showBackButton, which is what your UI is connected to.

You have two choices:

1)

$scope.$watch('globalServices.showBack', function(){
    $scope.showBackButton = globalServices.showBack;
}

This method involves monitoring changes to globalServices.showBack and updating $scope.showBackButton accordingly.

or

2)

$scope.globalServices = globalServices;

<a class="button-prev" ng-click="globalServices.back()" ng-show="globalServices.showBackButton">
    Back
</a>

In this approach, globalServices is directly exposed to your UI. This is my preferred way of handling it.

Answer №2

One reason for this behavior is that booleans are passed by value when assigned, making them a by-value type. So, when you write

$scope.showBackButton = globalServices.showBack;
, you are essentially assigning the value of $scope.showBackButton to the current value of globalServices.showBack. This means that any changes made to globalServices.showBack will not reflect in $scope.showBackButton.

To solve this issue, you can utilize an object which is assigned by reference:

app.factory('globalServices', function() {
    return {
        showButtonDetails: {
            showBack : false
        },
        back: function() {
            window.history.back();
        }
    };
});

<a class="button-prev" ng-click="back()" ng-show="showButtonDetails.showBack">
    Back
</a>

$scope.showButtonDetails = globalServices.showButtonDetails;
$scope.back = function() {
    globalServices.back();
};

globalServices.showButtonDetails.showBack = true;

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