Create empty promise in angular?

Question

I want to do something like this:

var promise = IAmAEmptyPromise;  if(condition){     promise = ApiService.getRealPromise(); }  promise.then(function(){     //do something }); 

So I want to declare a promise, which can be resolved using then. However this promise may be overwritten by another promise, which returns content. Later I want to resolve the promise whether it has content or not. Is this possible? I tried with:

var promise = $q.defer().promise;  if(!$scope.user){     promise = UserService.create(params); }  promise.then(function(){    //either user was created or the user already exists. }); 

However this does not work when a user is present. Any ideas?

Answer 1

Like Bixi wrote, you could use $q.when() which wraps a promise or a value into a promise. If what you pass to when() is a promise, that will get returned, otherwise a new promise is created which is resolved directly with the value you passed in. Something like this:

var promise; if(!$scope.user){   promise = UserService.create(params); } else {   promise = $q.when($scope.user); }  promise.then(function(user){   //either user was created or the user already exists. });