Is it possible to observe a collection of variables that are not within the current scope, but are still being utilized in Angular?

Question

Is it possible to observe a collection of variables that are not within the current scope, but are still being utilized in Angular?

Consider the following scenario with data coming from a service:

myService.var1
myService.var2
myService.var3

Typically, you would need to monitor each variable individually like this:

    $scope.$watch(function(){
      return myService.var1
    }, function(newValue, oldValue) {
    })

    $scope.$watch(function(){
      return myService.var2
    }, function(newValue, oldValue) {
    })

However, I am looking for a way to monitor all variables in one go.

I attempted the following methods, but encountered issues with each:

    // This resulted in a maximum digest cycle iteration error
    $scope.$watch(function(){
      return {
                 var1: myService.var1,
                 var2: myService.var2  
             }
    }, function(newValue, oldValue) {

    })

Additionally, I tried:

    $scope.myVar1 = myService.var1
    $scope.myVar2 = myService.var2
    // Unfortunately, this does not actually watch the service variables
    $scope.$watchGroup(['myVar1', 'myVar2'], function(newValue, oldValue) {

    })

Any suggestions on how to approach this?

javascript angularjs watch

Answer 1

Answer №1

To address the issue of maximum digest count, we need to take into consideration that creating a new instance of an object during each digest iteration is causing this problem. To resolve this, we can implement the following solution:

var watched = {
  var1: myService.var1,
  var2: myService.var2  
};
$scope.$watch(function(){
  return watched;
  // return angular.toJson(watched); // serialized can be better
}, function(newValue, oldValue) {
});

If you are using $watchGroup, you may encounter issues because you are watching copies of variables instead of the originals.

By following this adjusted approach, we can essentially revert back to the previous solution with some modifications:

$scope.vars = {var1: myService.var1, var2: myService.var2};
$scope.$watchGroup(['vars'], function(newValue, oldValue) {
});

Answer 2

To address the issue of maximum digest count, we need to take into consideration that creating a new instance of an object during each digest iteration is causing this problem. To resolve this, we can implement the following solution:

var watched = {
  var1: myService.var1,
  var2: myService.var2  
};
$scope.$watch(function(){
  return watched;
  // return angular.toJson(watched); // serialized can be better
}, function(newValue, oldValue) {
});

If you are using $watchGroup, you may encounter issues because you are watching copies of variables instead of the originals.

By following this adjusted approach, we can essentially revert back to the previous solution with some modifications:

$scope.vars = {var1: myService.var1, var2: myService.var2};
$scope.$watchGroup(['vars'], function(newValue, oldValue) {
});

Is it possible to observe a collection of variables that are not within the current scope, but are still being utilized in Angular?

Answer №1

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