AngularJS Angular promises with $q service Deferring operations using $q.defer
Example
We can use $q to defer operations to the future while having a pending promise object at the present, by using $q.defer we create a promise that will either resolve or reject in the future.
This method is not equivalent of using the $q constructor, as we use $q.defer to promisify an existing routine that may or may not return (or had ever returned) a promise at all.
Example:
var runAnimation = function(animation, duration) {
var deferred = $q.defer();
try {
...
// run some animation for a given duration
deferred.resolve("done");
} catch (err) {
// in case of error we would want to run the error hander of .then
deferred.reject(err);
}
return deferred.promise;
}
// and then
runAnimation.then(function(status) {}, function(error) {})
-
Be sure you always return a the
deferred.promiseobject or risk an error when invoking.then -
Make sure you always resolve or reject your deferred object or
.thenmay not run and you risk a memory leak
