The Angular scope remains static during service calculations and does not reflect immediate updates

Question

The Angular scope remains static during service calculations and does not reflect immediate updates

Is there a way to display a message on the scope indicating that a function in a service is currently being calculated and taking a long time? I have set up a simplified example in this jsfiddle: http://jsfiddle.net/rikboeykens/brwfw3g9/

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

app.service('testService', function(){
    this.longFunction=function(){
        for (var i=0; i<1000000000;i++){


        }
    }
});

function TestCtrl($scope, testService)
{
    $scope.$apply(function(){$scope.waiting="not waiting";});
    $scope.longFunction = function(){
        $scope.waiting="waiting";
        testService.longFunction();
        $scope.waiting="not waiting";
    }
}

The longFunction on the testService takes about two seconds to complete, but $scope.waiting is not updated to "waiting" while this is taking place.

I tried using $scope.$apply but then I just get an error saying $apply is already in progress.

Would it work if I perform the longFunction on the testService asynchronously? I have been looking into using promises but I'm not sure how I would go about implementing them.

javascript angularjs

Answer 1

Answer №1

Utilize the $timeout feature for better performance.

function ExampleCtrl($scope, exampleService, $timeout)
{
   $scope.status="not in progress";
    $scope.timeConsumingTask = function(){
        $scope.status="in progress";
        $timeout(function(){
          exampleService.performTask();
          $scope.status="not in progress";
        })
    }
}

Answer 2

Utilize the $timeout feature for better performance.

function ExampleCtrl($scope, exampleService, $timeout)
{
   $scope.status="not in progress";
    $scope.timeConsumingTask = function(){
        $scope.status="in progress";
        $timeout(function(){
          exampleService.performTask();
          $scope.status="not in progress";
        })
    }
}

Answer 3

Answer №2

The functionality is operational, however the waiting message may not be visible due to the synchronous execution of the longFunction, which hinders the UI from updating and displaying the waiting message. Once the longFunction call concludes, the UI becomes idle and displays the "not waiting" message rather than the expected "waiting" text.

This behavior is common in Web browsers as all operations take place within the UI thread, resulting in a freeze if activities are synchronous and causing a delay in refreshing the screen until the long operation completes. To overcome this, utilizing the setTimeout method within Angular can mimic an asynchronous process, allowing the UI to take precedence and reflecting the message change accordingly:

$scope.longFunction = function(){
        $scope.waiting="waiting"; 

        // This serves as a workaround, addressing the absence of a seamless way to queue asynchronous tasks within the JS UI layer. By the way, Web Workers could also be worth exploring in this context! ;)
        $timeout(function() {
            testService.longFunction();
        }, 0);

        $scope.waiting="not waiting";
}

Answer 4

The functionality is operational, however the waiting message may not be visible due to the synchronous execution of the longFunction, which hinders the UI from updating and displaying the waiting message. Once the longFunction call concludes, the UI becomes idle and displays the "not waiting" message rather than the expected "waiting" text.

This behavior is common in Web browsers as all operations take place within the UI thread, resulting in a freeze if activities are synchronous and causing a delay in refreshing the screen until the long operation completes. To overcome this, utilizing the setTimeout method within Angular can mimic an asynchronous process, allowing the UI to take precedence and reflecting the message change accordingly:

$scope.longFunction = function(){
        $scope.waiting="waiting"; 

        // This serves as a workaround, addressing the absence of a seamless way to queue asynchronous tasks within the JS UI layer. By the way, Web Workers could also be worth exploring in this context! ;)
        $timeout(function() {
            testService.longFunction();
        }, 0);

        $scope.waiting="not waiting";
}

Answer 5

Answer №3

Utilizing the $timeout function is essential for executing a service function. An illustrative example can be found on Codeopen.io: http://codepen.io/skymk/pen/EjNpKL?editors=101

app.controller('Controller', ['$scope', 'testService', '$timeout',  function($scope, testService, $timeout) {
    $scope.waiting="not waiting";
    $scope.longFunction = function() {
        $scope.waiting="waiting";
        $timeout(function() {
          testService.longFunction();
          $scope.waiting="not waiting";
        }, 0);    
    }
    $scope.longFunction()
}])

Answer 6

Utilizing the $timeout function is essential for executing a service function. An illustrative example can be found on Codeopen.io: http://codepen.io/skymk/pen/EjNpKL?editors=101

app.controller('Controller', ['$scope', 'testService', '$timeout',  function($scope, testService, $timeout) {
    $scope.waiting="not waiting";
    $scope.longFunction = function() {
        $scope.waiting="waiting";
        $timeout(function() {
          testService.longFunction();
          $scope.waiting="not waiting";
        }, 0);    
    }
    $scope.longFunction()
}])

The Angular scope remains static during service calculations and does not reflect immediate updates

Answer №1

Answer №2

Answer №3

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