I am having trouble in resolving a promise that is returned by firebase. This is an ionic - angularjs - firebase project that I am building to learn. The issue is that my function returns a promise that contains an array of 3 users but I am unable to unwrap this promise.
My code:
function eventusers(id) {
var userarr = [];
var deferred = $q.defer();
// *The code below makes 2 firebase calls and returns an array of users*
eventref.orderByChild("Eventid").equalTo(eventid).on("value", function(snap) {
var users = snap.val();
angular.forEach(users, function(value,key) {
var obj = value;
for (var prop in obj) {
if(obj[prop] == "True") {
userref.child(prop).on("value", function (snap) {
var id = snap.val().email;
userarr.push(id);
console.log(userarr); // I am able to see the list of users here
});
};
}
});
deferred.resolve(userarr);
});
return deferred.promise;
};
//The console.log shows a promise (pls see the attached pic)
console.log(eventusers(eventid));
// I tried to loop through the response using angular.forEach and also a for loop but it does
//not execute that part of the code as I do not see the response of the console.log. If I
//replace the for loop with just console.log(response), then I get an empty array.
eventusers(eventid).then(function (response) {
for (var i = 0; i <response.length; i++) {
console.log(response[i]);
}
});
Your deferred promise is resolving before the inner asynchronous action
userref.child(prop).on('value', ...
completes.
You'll need to wrap that in another deferred object then return a promise resolving all of the inner promises.
function eventusers(id) {
return $q(function(resolve) {
eventRef.orderByChild('Eventid').equalTo(id).on('value', function(snap) {
var promises = [];
snap.val().forEach(function(user) {
angular.forEach(user, function(userProp, prop) {
if (userProp === 'True') {
promises.push($q(function(resolve) {
userref.child(prop).on('value', function(snap) {
resolve(snap.val().email);
});
}));
}
});
});
resolve($q.all(promises));
});
});
}
eventusers(eventid).then(function (response) {
for (var i = 0; i < response.length; i++) {
console.log(response[i]);
}
});
Modify your code to
eventusers(eventid).then(function (response) {
var myArray = response.value;
for (var i = 0; i <myArray.length; i++) {
console.log(myArray[i]);
};
Since your array object is inside of promise object
You can also refer to Plunker
This is the service where im saving the data and returning the result
nurseService.js
(function () {
'use strict';
angular.module('app.services')
.factory('NurseService', NurseService);
NurseService.$inject = ['$http', '$q','Constants'];
function NurseService($http, $q, Constants){
var service = {
saveSample:saveSample
};
return service;
function saveSample(data) {
var deferred = $q.defer();
$http({method:"POST", data:data, url:Constants.API_URL_SAVE_SAMPLE_COLLECATION}).then(function(result){
return deferred.resolve(result.data);
});
};
return deferred.promise;
}
})();
This is the controller where im using the return value and based on the value returned im calling another http get method and printing it.
vm.saveSamples = function() {
var data = {
visitId: visitId,
orders: vm.gridTestApi.selection.getSelectedRows()
};
var url = Constants.API_URL_SAVE_SAMPLE_COLLECATION;
var barCodeResponse = null;
var sampleId = "";
var myDataPromise = NurseService.saveSample(data);
myDataPromise.then(function(result) {
console.log("data.name"+ JSON.stringify(result));
vm.printBarCode(result.sampleId);
// if(sampleId != ""){
printElement("printThisElement");
// }
});
//Barcode method this should call after saving the data and returned the sampleId
vm.printBarCode = function(sampleId) {
$http.get("master/barcode/"+sampleId).then(function (response) {
vm.barCodeImage = angular.copy(response.data.result);
});
}
But here before the saving print is calling. How can I hadle so that the first call should finish before the second http call to barcode and print it
//Print code
function printElement(elem) {
var printSection = document.getElementById('printSection');
// if there is no printing section, create one
if (!printSection) {
printSection = document.createElement('div');
printSection.id = 'printSection';
document.body.appendChild(printSection);
}
var elemToPrint = document.getElementById(elem);
// clones the element you want to print
var domClone = elemToPrint.cloneNode(true);
printSection.innerHTML = '';
printSection.appendChild(domClone);
window.print();
window.onafterprint = function () {
printSection.innerHTML = '';
}
};
You have to return the $http call in printBarCode and use a .then like so:
//Barcode method this should call after saving the data and returned the sampleId
vm.printBarCode = function(sampleId) {
return $http.get("master/barcode/"+sampleId).then(function (response) {
vm.barCodeImage = response.data.result;
});
}
myDataPromise.then(function(result) {
console.log("data.name"+ JSON.stringify(result));
return vm.printBarCode(result.sampleId)
}).then(
function() {
printElement("printThisElement");
},
function(error) {
// error handler
}
);
printElement will now wait for the printBarCode promise and .then to fulfil before executing.
You also don't have to use a $q.defer when doing a $http call, $http is already a promise so you can just return that like so:
function saveSample(data) {
return $http({method:"POST", data:data, url:Constants.API_URL_SAVE_SAMPLE_COLLECATION})
.then(
function(result) {
return result.data;
},
function(error) {
// don't forget to handle errors
}
);
}
First of all, $http internally implements promises you you dont have to explicitly create them.
Secondly, you should put all your http requests in the service/factory
The modified code looks like
angular.module('app.services')
.factory('NurseService', function($http){
var service = {
saveSample : function(data){
//first http implementation here
return $http.post(....);
}
getBarcode : function(sampleId){
//http implementation here for barcode
return $http.get(....);
}
}
return service;
});
and your controller can use the service like
angular.module('app.services')
.controller('saveSampleCtrl',function($scope,NurseService){
var postData = {
//your post data here
}
NurseService.saveSample(postData)
.then(function(data){
//read sampleId here from data
var sampleId = data.sampleId;
NurseService.getBarcode(sampleId)
.then(function(){
//your print statement here
});
});
}
there might be typos in the code but this is just a basic idea on how you could do that. Hope it helps
I want to unit test a function that is called multiple times based on a response from another function.
Similar to my question: Call a promise function multiple times until condition met from another promise function.
Here is the function
var monitorProgress = function() {
return getActiveTasks().then(function(res) {
if(res.length > 0) {
progress = res[0].progress;
if(progress !== 100){
return $timeout(function(){
return monitorProgress(); // multiple calls
},1000);
}
else {
// exit
console.log("done");
}
}
else{
console.log("done");
}
});
};
Here is how I tested this function:
describe('monitorProgress function', function() {
var response = null;
var promise = null;
var progress = 0;
beforeEach(function() {
// fake the implementation of monitorProgress
spyOn(SyncService,'monitorProgress').and.callFake(function() {
progress++;
// this mimics getActiveTasks promise and
// returns a promise with a res array length > 0
var deferred = $q.defer();
var res = [{ progress : progress }];
deferred.resolve(res);
// here the promise is returns
return deferred.promise.then(function(res) {
console.log("getActiveTasks res: " + JSON.stringify(res,null,2))
if(res.length > 0) {
progress = res[0].progress;
if(progress !== 100){
// keeps calling this until progress === 100
return SyncService.monitorProgress();
}
else {
// exit
console.log("exiting");
}
}
else {
// we never go here
}
});
});
// now that the spy is set, call the function
promise = SyncService.monitorProgress();
})
it("tracks that monitorProgress was called", function() {
expect(SyncService.monitorProgress).toHaveBeenCalled();
});
it("tracks that monitorProgress returned a promise", function() {
expect(promise).toBeDefined();
});
it("should return when progress is 100", function() {
// very important step
$rootScope.$apply();
// the final expectation
expect(progress).toBe(100);
});
});
I am having a method in my service as below.
module.service('Service', function($state, $rootScope) {
var getRemoteItems = function(page, displayLimit) {
var defferer = $q.defer()
var query = new Parse.Query("Item");
query.limit(displayLimit);
query.skip(page * displayLimit);
query.descending("createdAt");
var items = [];
query.find({
success: function(results) {
//process results
return results;
},
error: function(e) {
return null;
}
});
}
}
Although it's working, I am trying to make changes so that in the controller which calls this method, can use success and failure checks instead of doing it in the service method.
I am not able to understand how to use promises in this example. I am expecting somehting like below.
Service.getRemotItems(1,10).then()...error()..
Please excuse me for any syntax issues in the example as I am new to Angular.
You've already created the promise with $q.defer() you just need to resolve/reject it in the success & error callbacks
module.service('Service', function($state, $rootScope, $q) {
var getRemoteItems = function(page, displayLimit) {
var deferred = $q.defer();
var query = new Parse.Query("Item");
query.limit(displayLimit);
query.skip(page * displayLimit);
query.descending("createdAt");
var items = [];
query.find({
success: function(results) {
deferred.resolve(results);
},
error: function(e) {
deferred.reject(e);
}
});
return deferred.promise;
}
}
I've been trying to wait for a couple of promises with Angular's $q but there seems to be no option to 'wait for all even when a promis is rejected'.
I've created an example (http://jsfiddle.net/Zenuka/pHEf9/21/) and I want a function to be executed when all promises are resolved/rejected, is that possible?
Something like:
$q.whenAllComplete(promises, function() {....})
EDIT: In the example you see that the second service fails and immediately after that the function in $q.all().then(..., function(){...}) is being executed. I want to wait for the fifth promise to be completed.
Ok, I've implemeted a basic version myself (I only want to wait for an array of promises). Anyone can extend this or create a cleaner version if they want to :-)
Check the jsfiddle to see it in action: http://jsfiddle.net/Zenuka/pHEf9/
angular.module('test').config(['$provide', function ($provide) {
$provide.decorator('$q', ['$delegate', function ($delegate) {
var $q = $delegate;
// Extention for q
$q.allSettled = $q.allSettled || function (promises) {
var deferred = $q.defer();
if (angular.isArray(promises)) {
var states = [];
var results = [];
var didAPromiseFail = false;
if (promises.length === 0) {
deferred.resolve(results);
return deferred.promise;
}
// First create an array for all promises with their state
angular.forEach(promises, function (promise, key) {
states[key] = false;
});
// Helper to check if all states are finished
var checkStates = function (states, results, deferred, failed) {
var allFinished = true;
angular.forEach(states, function (state, key) {
if (!state) {
allFinished = false;
}
});
if (allFinished) {
if (failed) {
deferred.reject(results);
} else {
deferred.resolve(results);
}
}
}
// Loop through the promises
// a second loop to be sure that checkStates is called when all states are set to false first
angular.forEach(promises, function (promise, key) {
$q.when(promise).then(function (result) {
states[key] = true;
results[key] = result;
checkStates(states, results, deferred, didAPromiseFail);
}, function (reason) {
states[key] = true;
results[key] = reason;
didAPromiseFail = true;
checkStates(states, results, deferred, didAPromiseFail);
});
});
} else {
throw 'allSettled can only handle an array of promises (for now)';
}
return deferred.promise;
};
return $q;
}]);
}]);
Analogous to how all() returns an array/hash of the resolved values, the allSettled() function from Kris Kowal's Q returns a collection of objects that look either like:
{ state: 'fulfilled', value: <resolved value> }
or:
{ state: 'rejected', reason: <rejection error> }
As this behavior is rather handy, I've ported the function to Angular.js's $q:
angular.module('your-module').config(['$provide', function ($provide) {
$provide.decorator('$q', ['$delegate', function ($delegate) {
var $q = $delegate;
$q.allSettled = $q.allSettled || function allSettled(promises) {
// Implementation of allSettled function from Kris Kowal's Q:
// https://github.com/kriskowal/q/wiki/API-Reference#promiseallsettled
var wrapped = angular.isArray(promises) ? [] : {};
angular.forEach(promises, function(promise, key) {
if (!wrapped.hasOwnProperty(key)) {
wrapped[key] = wrap(promise);
}
});
return $q.all(wrapped);
function wrap(promise) {
return $q.when(promise)
.then(function (value) {
return { state: 'fulfilled', value: value };
}, function (reason) {
return { state: 'rejected', reason: reason };
});
}
};
return $q;
}]);
}]);
Credit goes to:
Zenuka for the decorator code
Benjamin Gruenbaum for pointing me in the right direction
The all implementation from Angular.js source
The promise API in angularJS is based on https://github.com/kriskowal/q. I looked at API that Q provides and it had a method allSettled, but this method has not been exposed over the port that AngularJS uses. This is form the documentation
The all function returns a promise for an array of values. When this
promise is fulfilled, the array contains the fulfillment values of the
original promises, in the same order as those promises. If one of the
given promises is rejected, the returned promise is immediately
rejected, not waiting for the rest of the batch. If you want to wait
for all of the promises to either be fulfilled or rejected, you can
use allSettled.
I solved this same issue recently. This was the problem:
I had an array of promises to handle, promises
I wanted to get all the results, resolve or reject
I wanted the promises to run in parallel
This was how I solved the problem:
promises = promises.map(
promise => promise.catch(() => null)
);
$q.all(promises, results => {
// code to handle results
});
It's not a general fix, but it is simple and and easy to follow. Of course if any of your promises could resolve to null then you can't distinguish between that a rejection, but it works in many cases and you can always modify the catch function to work with the particular problem you're solving.
Thanks for the inspiration Zenuka, you can find my version at https://gist.github.com/JGarrido/8100714
Here it is, in it's current state:
.config( function($provide) {
$provide.decorator("$q", ["$delegate", function($delegate) {
var $q = $delegate;
$q.allComplete = function(promises) {
if(!angular.isArray(promises)) {
throw Error("$q.allComplete only accepts an array.");
}
var deferred = $q.defer();
var passed = 0;
var failed = 0;
var responses = [];
angular.forEach(promises, function(promise, index) {
promise
.then( function(result) {
console.info('done', result);
passed++;
responses.push(result);
})
.catch( function(result) {
console.error('err', result);
failed++;
responses.push(result);
})
.finally( function() {
if((passed + failed) == promises.length) {
console.log("COMPLETE: " + "passed = " + passed + ", failed = " + failed);
if(failed > 0) {
deferred.reject(responses);
} else {
deferred.resolve(responses);
}
}
})
;
});
return deferred.promise;
};
return $q;
}]);
})
A simpler approach to solving this problem.
$provide.decorator('$q', ['$delegate', function ($delegate) {
var $q = $delegate;
$q.allSettled = $q.allSettled || function (promises) {
var toSettle = [];
if (angular.isArray(promises)) {
angular.forEach(promises, function (promise, key) {
var dfd = $q.defer();
promise.then(dfd.resolve, dfd.resolve);
toSettle.push(dfd.promise);
});
}
return $q.all(toSettle);
};
return $q;
}]);
A simple solution would be to use catch() to handle any errors and stop rejections from propagating. You could do this by either not returning a value from catch() or by resolving using the error response and then handling errors in all(). This way $q.all() will always be executed. I've updated the fiddle with a very simple example: http://jsfiddle.net/pHEf9/125/
...
function handleError(response) {
console.log('Handle error');
}
// Create 5 promises
var promises = [];
var names = [];
for (var i = 1; i <= 5; i++) {
var willSucceed = true;
if (i == 2) willSucceed = false;
promises.push(
createPromise('Promise' + i, i, willSucceed).catch(handleError));
}
...
Be aware that if you don't return a value from within catch(), the array of resolved promises passed to all() will contain undefined for those errored elements.
just use finally
$q.all(tasks).finally(function() {
// do stuff
});