Any way to know if a variable is an angularjs promise?

Question

I\'m making a directive that takes a function as a scope parameter (scope: { method:\'&theFunction\' }). I need to know if the result returned by that metho

Answer 1

The $q.when() answer seems like the best answer for most use cases, I used instanceof for mine.

    if(buttonData instanceof $q) {
        buttonData.then(function(actions) {
            $scope.buttonActions = actions;
        });
    } else {
        $scope.button = buttonData;
    }

Alternatively, the following IF worked as well, but I ended up going with the above solution.

if(Object.getPrototypeOf(buttonData) === $q.prototype) {

Answer 2

@kayakDave, thanks for guiding to right place.

angular $q

when(value, [successCallback], [errorCallback], [progressCallback]);
            Wraps an object that might be a value or a (3rd party) then-able promise into a $q promise. 
            This is useful when you are dealing with an object that might  or might not be a promise, 
            or if the promise comes from a source that can't be trusted.

$q.when(value).then(function (data) {
//this helps me to bind data from $resource or $http or object
}

check this fiddle

Answer 3

Angular's when() is a good option as Davin mentioned.

If that doesn't meet your needs then Angular's internal way of checking (it uses this inside when) is very close to what you're doing:

var ref = function(value) {
   if (value && isFunction(value.then)) {
      // Then this is promise
   }

Answer 4

You can use $q.when to wrap the object as a promise (whether it is or not). Then, you can be sure that you are always dealing with a promise. This should simplify the code that then handles the result.

Documentation for $q.when is here with $q.