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variable is not accessible in angular.forEach

Posted by: admin November 30, 2017 Leave a comment

Questions:

I have a service

app.service('myService', function() {
    this.list = [];
    this.execute = function() {
        //this.list is reachable here
        angular.forEach(AnArrayHere, function(val, key) {
           //this.list is not reachable here
        });
    }
}

even in controller its accessible

function Ctrl($scope, myService) {
    $scope.list = myService.list;
}

Can someone explain me why “this.list” is not reachable within the angular.foreach and how can I access to “this.list” ?

Answers:

The last parameter in the angular.forEach (See http://docs.angularjs.org/api/angular.forEach) function is the context for this. So you’ll want something like this:

app.service('myService', function() {

    this.list = [];

    this.execute = function() {

        //this.list is reachable here

        angular.forEach(AnArrayHere, function(val, key) {
           //access this.list
        }, this);

    }
}

Questions:
Answers:

The reason this.list is not accessible in the foreach is because the context for that function call has changed. It works inside the execute method as that method is part of the same context as list.

Due to all the closures I would assign the this context to another variable that you can then call later on. Something like this:

app.service('myService', function() {

    var self = this;
    self.list = [];

    self.execute = function() {
        //this.list and self.list are reachable here
        angular.forEach(AnArrayHere, function(val, key) {
           //self.this == this.list
        });
    }
}

This is a slightly more general solution than passing the context as part of the foreach method call and would work in other closure related situations.