angularjs strange array behaviour, probably related to asynchronous execution?

Question

Difficult to reproduce, so I will try to explain instead.

Within a factory of angularjs I have a function like this

angular.module('my').factory('Database', ['$window', 'Raw', function($window, Raw) {
    return {
        read: function() {

where Raw is another factory defined below that returns a data string

Then I do this:

var lines = [];
lines = Raw.data.split("*");

which gives me an array of strings.

The strange behaviour is that it gives an error as lines[0] is undefined. I can solve this error by adding an alert

var lines = [];
lines = Raw.data.split("*");
alert(lines[0])

which shows me the expected string. But it does not work if I put a console.log command instead.

So, what's going on??

Cheers,

please post Raw.data code

Maxim Shoustin
– Maxim Shoustin

2014-02-12 10:53:30 +00:00
Commented Feb 12, 2014 at 10:53 — Maxim Shoustin
– Maxim Shoustin, Commented Feb 12, 2014 at 10:53

Maxim Shoustin · Accepted Answer · 2014-02-12 12:26:29Z

1

Sounds like you get Raw.data by async way and when you try split it, it still undefined.

If Raw.data returns promise, use then() callback than, something like:

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

myModule.controller('myController', ['$scope', 'Database', function($scope, Database) {
   $scope.text =  Database.read();    
}]);

myModule.factory('Database', ['$window', 'Raw', '$q', function($window, Raw, $q) {

  return {
 read: function() {
         var deferred=$q.defer();
        Raw.data().then(function(data) {
            lines = data.split("*");
          deferred.resolve(lines); 
        });
        return deferred.promise;
     }
   }    
}]);

myModule.factory('Raw', ['$window', '$q', function($window, $q) {
    return {
        data: function() {
            var data = "blah * blah";
            var deferred = $q.defer();              
                deferred.resolve(data);               
                return deferred.promise;
        }
    }
}]);

Demo Fiddle

edited Feb 12, 2014 at 12:26

answered Feb 12, 2014 at 10:52

Maxim Shoustin

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3 Comments

GWorking Over a year ago

I didn't know about promises, very interesting (thanks). Then, Raw is a factory that returns the string "data". In order to make it to return a promise, should I make a function then? Or is there any other way?

Maxim Shoustin Over a year ago

please post the data structure and ill post Fiddle example how it should work with promises

GWorking Over a year ago

Thanks a lot! And I see that you add a 2nd promise because you cannot leave a factory without a return value, so if you want to return what is inside the "then" function, then you need a promise. Much clearer now, thanks!!

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