Return nested promise to parent function

Question

In most angularjs tutorials I've seen promise chains result in changing a scope variable.

$http.get(someURL).then(function (value) {
    $scope.someValue = value;
});

Is it possible to return that value to a parent function? Ever method I've tried just returns another promise.

$scope.test = function(){
    return $http.get(someURL).then(function (value) {
        return value;
    });
};

$scope.test = function(){
    var deferred = $q.defer();
    $http.get(someURL).then(function (value) {
        deferred.resolve(value);
    });
  return deferred.promise;
}

I don't want to chain another promise, just return the json so I can do something like this:

<button ng-click='some_vars = test()'>Get ajax</button>
<ul ng-repeat='var in some_vars'>
    <li>{{var.title}}</li>
</ul>

No, because you can't return from AN AJAX call - you can still set a scope variable to the result of an AJAX call and the view will auto update. — tymeJV
– tymeJV, Commented Oct 17, 2014 at 19:46
@tymeJV that's not true, depends on the version that the OP is using, promise unwrapping has been deprecated and I would never advice anyone to do that, but in Anular 1.2 it's still possible to change the settings of the $parseProvider, like this: $parseProvider.unwrapPromises(true); — Josep
– Josep, Commented Oct 17, 2014 at 20:34
embed a defer inside a promise is an antipattern github.com/petkaantonov/bluebird/wiki/Promise-anti-patterns i know that's on the server side, but you can take it as a reference — pedrommuller
– pedrommuller, Commented Oct 17, 2014 at 20:34

Josep · Accepted Answer · 2014-10-17 20:39:18Z

3

IMO this is how you should do it:

In your controller do this:

$scope.some_vars=[];
$scope.loadVars = function(){
    $http.get(someURL).success(function (data) {
        $scope.some_vars=data;
    });
};

In your view do this:

<button ng-click='loadVars()'>Get ajax</button>
<ul ng-if="some_vars.length>0" ng-repeat='var in some_vars'>
    <li>{{var.title}}</li>
</ul>

Much easier, right?

However if you are using a version of Angular prior to 1.2.0-rc.3. and you really want to automatically unwrap the promises (I would strongly advise you against that), you would have to change the settings of the $parseProvider in the config of your module, like this:

.config(function($parseProvider){
  $parseProvider.unwrapPromises(true);
})

Working Example

Promise unwrapping was removed with version 1.2 and it has been completely deprecated with version 1.2.0-rc.3.

You may want to have a look at this document: Migrating from Previous Versions.

$parse: due to fa6e411d, promise unwrapping has been removed. It has been deprecated since 1.2.0-rc.3. It can no longer be turned on. Two methods have been removed:
     $parseProvider.unwrapPromises 

     $parseProvider.logPromiseWarnings

edited Oct 17, 2014 at 20:39

answered Oct 17, 2014 at 20:00

Josep

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3 Comments

Bill Johnston Over a year ago

I get that you can do it this way, but it is truly IMPOSSIBLE to just return the value? I want to avoid having to make a bunch of different functions that control how to update the scope, prefer to just do it in the html.

Josep Over a year ago

@BillJohnston no, it's not impossible, I will update my answer in a sec, but I would advise you against it.

Josep Over a year ago

@BillJohnston I've updated my answer, please have a look at it, thanks!

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