I have an AngularJS service with such async API:
myService.asyncCall(['id0', 'id3', 'id2']).then(function (complexData) {
// handle complexData
}).catch(function (error) {
console.log(error);
});
asyncCall incapsulates multiple calls of $http which handled by $q.all. Each of the $http requests can response with error and I want the errors to be handled by one catch handler. So how i can achieve multiple calls of the catch handler ?
If I understood correctly (finally), this is what you are trying to achieve:
$q.all should be "augmented" to suit your needs, because by default:
Here is a possible implementation:
function asyncCall(listOfPromises, onErrorCallback, finalCallback) {
listOfPromises = listOfPromises || [];
onErrorCallback = onErrorCallback || angular.noop;
finalCallback = finalCallback || angular.noop;
// Create a new list of promises that can "recover" from rejection
var newListOfPromises = listOfPromises.map(function (promise) {
return promise.catch(function (reason) {
// First call the `onErrroCallback`
onErrorCallback(reason);
// Change the returned value to indicate that it was rejected
// Based on the type of `reason` you might need to change this
// (e.g. if `reason` is an object, add a `rejected` property)
return 'rejected:' + reason;
});
});
// Finally, we create a "collective" promise that calls `finalCallback` when resolved.
// Thanks to our modifications, it will never get rejected !
$q.all(newListOfPromises).then(finalCallback);
}
See, also, this short demo.
all modification?
finalCallback. E.g. replace .then(finalCallback) with .then(function(results){finalCallback(results.filter(function(res){return res.indexOf('rejected:') !== 0;}));}).
onErrorCallback() is called and check it before calling finalCallback. It really depends on your exact requirements.One way, would be to attach a .catch handler indidually in your service:
function asyncCall(urls){
var calls = urls.map(makeSomeCall).
map(function(prom){ return prom.catch(e){ /* recover here */});
return $q.all(calls);
};
Another way would be to implement a settle method that is like $q.all but keeps track of all results. Stealing from my answer here:
function settle(promises){
var d = $q.defer();
var counter = 0;
var results = Array(promises.length);
promises.forEach(function(p,i){
p.then(function(v){ // add as fulfilled
results[i] = {state:"fulfilled", promise : p, value: v};
}).catch(function(r){ // add as rejected
results[i] = {state:"rejected", promise : p, reason: r};
}).finally(function(){ // when any promises resolved or failed
counter++; // notify the counter
if (counter === promises.length) {
d.resolve(results); // resolve the deferred.
}
});
});
})
You can handle multiple promises as such:
var promiseArr = ["id0","id3","id2"].map(makePromise);
settle(promiseArr).then(function(results){
var failed = results.filter(function(r){ return r.state === "rejected"; });
var failedValues = failed.map(function(i){ return i.value; });
var done = results.filter(function(r){ return r.state === "fulfilled"; });
var doneValues = done.map(function(i){ return i.value; });
});
Which gives you access to all results of the promise, regardless if it failed or not, and let you recover with more granularity.
Your service should handle that aggregation since it's the one returning a promise on everything. One example would be to do:
if(failed.length > 0){
throw new Error("The following failed..."); // some info about all failed
}
$http answers with error ? That is why i want multiple calls of catch
then handler will not be called if at least one of promises will be rejected (because of all behaviour). In other words in need kind of all that will call then for all resolved promises and catch for each rejected promise.
$q.allgets rejected when any of the promises gets rejected. What exactly are you trying to achieve ?$q.all$q.all. I want myasyncCall1. to get array of promises, 2. has one resolve handler for each resolved promise from the array (thenblock from the example) 3. has one reject handler that will be called for each rejected promise. (catchblock from the example). I hope now it is clear.