Updated with HTTP and initial code based on requests/Please look at the bottom of the post:
I've been posting several questions on my AngularJS learning curve of late and the SO community has been fantastic. I've been a traditional C programmer when I used to program and have recently started writing my own ionic/Angular JS app. I'm struggling with the promise version of traditional async calls when it comes to converting a custom function to a promise. I don't think I really understood and I find various examples very contrived. I'd appreciate some help. I have some code which is not working, and I have some conceptual questions:
Let's take this simple function:
angular.module('zmApp.controllers').service('ZMDataModel', function() { return { getMonitors: function () { return monitors; } }
getMonitors is a simple function that basically returns an array of monitors. But here is the rub: When the app first starts, I call an http factory that does an http get and goes about populating this monitor list. This http factory is different from this service but invokes a setMonitor method in this service to populate the array. When the array is populated, a variable called 'monitorsLoaded' is set to 1. When this variable is set to 1, I know for sure monitors is loaded.
Now, I have a view with a controller called "MontageCtrl". I want to wait for the monitors to load before I show the view. In a previous post, one person suggested I use route resolve, but I had to first convert my getMonitors to a promise. So here is what I did:
angular.module('zmApp.controllers').service('ZMDataModel', function($q) {
getMonitors: function () {
var _deferred = $q.defer();
if (monitorsLoaded!=0)
{
console.log ("**** RETURNING MONITORS *****");
_deferred.resolve(monitors);
}
console.log ("*** RETURNING PROMISE ***");
return _deferred.promise;
},
Next up, in app.js I connected the route as follows:
.state('app.montage', {
data: {requireLogin:false},
resolve: {
message: function(ZMDataModel)
{
console.log ("Inside app.montage resolve");
return ZMDataModel.getMonitors();
}
},
Finally I modified my controller to grab the promise as such:
angular.module('zmApp.controllers').controller('zmApp.MontageCtrl', function($scope,$rootScope, ZMHttpFactory, ZMDataModel,message) {
//var monsize =3;
console.log ("********* Inside Montage Ctrl");
It seems based on logs, I never go inside Montage Ctrl. Route resolve seems to be waiting for ever, whereas my logs are showing that after a while, monitorLoaded is being set to 1.
I have several conceptual questions:
a) In function getMonitors, which I crafted as per examples, why do people return a _deferred.promise but only assign a _deferred.resolve? (i.e. why not return it too?). Does it automatically return?
b) I noticed that if I moved var _deferred definition to my service and out of its sub function, it did work, but the next view that had the same route dependency did not. I'm very confused.
c) Finally I ready somewhere that there is a distinction between a service and a factory when it comes to route resolve as a service is only instantiated once. I am also very confused as in some route resolve examples people use when, and I am using .state.
At this stage, I'm deep into my own confusion. Can someone help clarify? All I really want is for various views to wait till monitorsLoaded is 1. And I want to do it via route resolves and promises, so I get the hang of promises once and for all.
Added: Here is the HTTP factory code as well as the app.run code that calls this when the app first starts. FYI, the http factory works well - the problems started when I crafted ZMDataModel - I wanted this to be a central data repository for all controllers to use -- so they did not have to call HTTP Factory each time to access data, and I could control when HTTP factory needs to be called
angular.module('zmApp.controllers').factory('ZMHttpFactory', ['$http', '$rootScope','$ionicLoading', '$ionicPopup','$timeout','ZMDataModel',
function($http, $rootScope, $ionicLoading, $ionicPopup, $timeout,ZMDataModel) {
return {
getMonitors: function() {
var monitors = [];
var apiurl = ZMDataModel.getLogin().apiurl;
var myurl = apiurl+"/monitors.json";
return $http({
url: myurl,
method: 'get'
}) //http
.then(function(response) {
var data = response.data;
//console.log("****YAY" + JSON.stringify(data));
// $rootScope.$broadcast ('handleZoneMinderMonitorsUpdate',monitors);
$ionicLoading.hide();
ZMDataModel.setMonitors(data.monitors);
ZMDataModel.setMonitorsLoaded(1);
//monitors = data.monitors;
return ZMDataModel.getMonitors();
},
function (result)
{
console.log ("**** Error in HTTP");
$ionicLoading.hide();
ZMDataModel.setMonitorsLoaded(1);
//$ionicPopup.alert ({title: "Error", template:"Error retrieving Monitors. \nPlease check if your Settings are correct. "});
return ZMDataModel.getMonitors();
}
); //then
}, //getMonitors
And here is the code in app.run that first calls this:
.run(function($ionicPlatform, $ionicPopup, $rootScope, $state,ZMDataModel, ZMHttpFactory)
{
ZMDataModel.init();
var loginData = ZMDataModel.getLogin();
if ( loginData.username && loginData.password && loginData.url && loginData.apiurl)
{
console.log ("VALID CREDENTIALS. Grabbing Monitors");
// this calls http factory getMonitors that eventually populated the ZMDataModel
// monitors array and sets monitorsLoaded to 1
ZMHttpFactory.getMonitors();
}
}
I finally solved all the problems. There were various issues with my initial attempts. My final resolved solution is here Am I returning this promise correctly?
The learnings:
a) Separating the HTTP get into a factory and the data model into another service was unnecessarily complicating life. But that separation was not the problem. Infact, the way the promise was coded above, on first run, if monitorsLoaded was 0, it would simply return the deferred promise and there was no ".success" or similar construct for me to get into the resolve code block again.
b) The biggest thing that was making me run around in loops was deferring or rejecting was simply setting a state. the return always has to be the promise - and it would return the state you set. I assumed return d.promise always means returning "in progress".
Related
Thanks in advance for the help...
I have a controller I'm using to call an API to send a password reset link. I have abstracted the actual $http call off into a service to keep the controller thin. Originally I was doing something like this:
angular.module('module')
.service('forgotPasswordService', ['$http', function($http) {
$http(request).then(function() {
return {}; //return some object using response
}]);
I felt like this would be the best approach as it would keep the controller as thin as possible and kept all service related actions separate. My problem with this was that returning from within the promise never actually returned me anything. I had to actually return the $http service call to get the promise. The only way I was able to make all of this work was if I called .then from within the controller.
//controller
angular.module('module')
.controller('forgotPasswordCtrl', ['forgotPasswordService', function(forgotPasswordService) {
forgotPasswordService.forgotPassword(emailAddress).then(function() {
//do stuff
}
}]);
//service
angular.module('module')
.service('forgotPasswordService', ['$http', function($http){
this.forgotPassword = function(emailAddress) {
return $http(request);
};
}]);
This just feels a little wrong to me because the controller now depends on receiving a promise back from the service. I may just be overthinking this but I would like a second opinion.
Is this considered acceptable/good practice? Is there an alternative to this which would allow me to achieve the encapsulation I'm looking for?
Thanks again.
I've interfaced with the $http from the controller in two slightly different ways.
Like you it felt wrong returning the $http from the service and interfacing with it.
So first I created services and passed in a success method and an error method (callbacks).
// Service
angular.module('module')
.service('forgotPasswordService', ['$http', function($http) {
function sendForgotPasswordEmail(emailAddress, success, error){
$http.post('/api/v1/resetpassword', {emailAddress:emailAddress})
.then(success, error);
}
return {
sendForgotPasswordEmail: sendForgotPasswordEmail
}
}]);
// Controller
angular.module('module')
.controller('forgotPasswordCtrl', ['forgotPasswordService', function(forgotPasswordService) {
forgotPasswordService.sendForgotPasswordEmail(emailAddress,
function(response){ //success
// notify user of success
},
function(response){ // error
// notify user of error
});
}]);
This worked great. I created an large application this way, but as I started on my second large angular project I wondered why I was hiding the $http's promise?
By passing back the promise, I can use other libraries that support promises. With my first approach I can't leverage other libraries promise support.
Passing back the $http promise
// Service
angular.module('module')
.service('forgotPasswordService', ['$http', function($http) {
function sendForgotPasswordEmail(emailAddress){
return $http.post('/api/v1/resetpassword', {emailAddress:emailAddress});
}
return {
sendForgotPasswordEmail: sendForgotPasswordEmail
}
}]);
// Controller
angular.module('module')
.controller('forgotPasswordCtrl', ['forgotPasswordService', function(forgotPasswordService) {
forgotPasswordService.sendForgotPasswordEmail(emailAddress)
.then(
function(response){ //success
// notify user of success
},
function(response){ // error
// notify user of error
});
}]);
I deleted my original answer, and I feel like a dork for stating that you could do it the other way. When I went back and checked my original code back when I first started angular, I found that I was calling then() twice in my application - once in my service where I returned the data, and once in my controller because calling $http(request).then() returns a promise.
The fact is, you're dealing with an asynchronous call. Suppose in your controller, you wanted to do this:
$scope.foo = myService.getFoo(); // No then()
The XmlHttpRequest inside the $http in getFoo() is an asynchronous call, meaning that it calls it and moves on. The synchronous option is deprecated. It's bad practice to make a blocking synchronous HTTP call because it will seize up your UI. This means you should use a callback when the data is ready, and the promise API is made just for that.
If you absolutely do not want to use the then() in your controller, I suppose you could probably pass your scope binding parameters to your service and let your service update them in your then call. I haven't tried this, and because it's asynchronous, I'm not sure if angular will know to call a digest() so you may need to call a $scope.$apply() if the values don't update. I don't like this, because I think the control of the values in the scope should be handled by the controller and not the service, but again - it's your personal preference.
Sorry for leading you astray with my initial answer - I ran into the same question you had, but when I looked back - I saw I used a silly solution.
-- Relevant statements in original answer --
Consider the following:
Where do you want your error handling for the call and who needs to know about it?
Do you need to handle specific failures in a particular controller or can they all be grouped together to one error handler? For some apps, I like to display the errors in a particular place rather than in a general modal dialog, but it's acceptable to create a service to handle all errors and pop them up for the user.
Where do you want to handle your progress/busy indicator?
If you have an interceptor wired up for all http calls and broadcasting an event to show/hide the busy indicator, then you don't need to worry about handling the promise in the controller. However some directives will use the promise to show a busy indicator which requires you to bind it to the scope in the controller.
To me, the decision is determined by the requirements and by personal choice.
Try using a callback like so:
angular.module('module')
.service('forgotPasswordService', ['$http', function($http) {
var recovery = function(request, callback) {
$http(request).then(function(response) {
callback(response);
})
}
return { recovery: recovery }
}]);
Then you would call it like this:
forgotPasswordService.recovery('http://...', function(response){
console.log(response);
})
I'm running into a bit of a problem with an Angular (1.4) service. The code is roughly as follows :
service.retrieveStuffFromServer = function() {
return httpCallFromServer().then(
function(data) {
if (Array.isArray(data)) {
return data;
}
return [];
}
);
};
I call this function in two distinct controllers. Most of the times, it works as intended, but I'm having problem in those conditions :
The HTTP call takes time to return the data
Controller A calls the service.
Controller B calls the service.
The service returns data to controller A
The call in the controller B is cancelled. The logic after it never executes
My first guess would be to slightly alter the service, to inform either of the controllers if the service is already busy so I can retry later, but I'm not sure if this is the best solution, so I'm looking for some advice.
Hard to say why it doesn't just work, but presumably something in httpCall() is preventing the same call from being made again before the 1st one completes, and it rejects if that happens. But if you want controller B call to share the response from an active previous call, you could cache the promise:
function myFunction() {
if (!myFunction.promise) {
myFunction.promise = httpCall()
.then(function(result) {
myFunction.promise = undefined;
return ...
}, function(err) {
myFunction.promise = undefined;
throw err;
});
}
return myFunction.promise;
}
This will cause the same promise from a prior call to be returned as long as the prior call is still unresolved.
Using a property of the function itself as a cache is a convenient way to keep state associated logically with the function itself. You could just use any variable defined outside the scope of myFunction though.
I have a service with a method that gets me a list of project types using a $resource. It's working well for me, except that if I make multiple nearly simultaneous calls (from say, two directives) each will create another request instead of using the same response/$promise/data.
I found this which led me to this and TL;DR, apparently it's creating a redundant $q.defer() and is actually considered to be a deferred anti-pattern.
The code below works well if the calls to get project types are significantly staggered (like more than milliseconds apart). The consecutive calls are resolved with the shared.projectTypes. It also works in the sense that if the request to get project types fails, the dfr.reject() will be triggered and be caught by .catch in the calling controller.
angular.module('projects')
.factory('projectService', function(notificationService){
// an object to share data gathered by this service
var shared = {};
// $resource for projects API
var projectResource = $resource(baseApiPath + 'projects', {}, {
...,
getProjectTypes: {
method: 'GET',
url: baseApiPath + 'projects/types'
},
...
});
// loads a list of project types
var loadProjectTypes = function(){
var dfr = $q.defer();
// if we've already done this, just return what we have.
if(shared.projectTypes){
dfr.resolve(shared.projectTypes);
}
else {
// begin anti-pattern (?)
projectResource.getProjectTypes(null,
function(response){
shared.projectTypes = response.result.projectTypes;
dfr.resolve(response);
},
function(errResponse){
console.error(errResponse);
notificationService.setNotification('error', errResponse.data.messages[0]);
dfr.reject(errResponse);
});
}
return dfr.promise;
};
return {
shared: shared,
project: projectResource,
loadProjectTypes: loadProjectTypes
};
});
So, I read that having this extra var dfr = $q.defer() is not necessary as the $resource would provide all that for me. With a bit of refactoring, I ended up with this:
...
// $resource for projects API
var projectResource = $resource(baseApiPath + 'projects', {}, {
...,
getProjectTypes: {
method: 'GET',
url: baseApiPath + 'projects/types',
isArray: true,
transformResponse: function(response){
return JSON.parse(response).result.projectTypes;
}
},
...
});
// loads a list of project types
var loadProjectTypes = function(){
return shared.projectTypes || (shared.projectTypes = projectResource.getProjectTypes());
};
...
To clarify, I have added isArray and transformResponse to the resource because my API returns a lot of extra meta information and all I wanted was an array of types. In my loadProjectTypes method, I'm including the same caching we originally had, but I'm caching the result of projectResource.getProjectTypes() instead of the actual response data (even though that might be exactly what I'm caching because of the transformResponse).
This works on the happy path (reduced calls to API, returns the same thing to everyone, etc) but my main problem is with the chaining and catching of errors.
In my original anti-pattern example, if there is an error with GET /project/types, I'm using dfr.reject() which is then passed back to my controller where I have a .catch().
This is code from the controller which actually makes the original request to get project types:
$q.all([
projectService.loadProjects(),
userService.loadUserRole('project_manager'),
userService.loadUserRole('sales_representative'),
projectService.loadProjectTypes(),
clientService.loadClients()
])
.then(function(response){
// doing stuff with response
})
.catch(function(errResponse){
// expecting errors from service to bubble through here
console.error(errResponse);
});
With the anti-pattern example, the dfr.reject is causing the error to show up here in the catch, but in my supposed non-anti-pattern example, it's not happening. I'm not sure how to reject or resolve the $resource results in the same way I was before. If one of the points of promise chaining is to have one spot to handle errors from any chain link, I was doing it right.
I tried to use $q.resolve()/reject(), since I don't have dfr anymore, but this seems dumb and doesn't work anyway.
return shared.projectTypes || (shared.projectTypes = projectResource.getProjectTypes(null,
function(response){
return $q.resolve(response);
},
function(errResponse){
return $q.reject(errResponse);
}));
How do I get the chain to work so that .catch() in the controller is where the errors get handled?
Did I actually implement the anti-pattern in my original code, or was that one of the accepted ways to use $q.defer() and it wasn't an anti-pattern at all?
In the second link I posted, there is an answer that says:
"What's wrong with it? But the pattern works! Lucky you.
Unfortunately, it probably doesn't, as you likely forgot some edge
case. In more than half of the occurrences I've seen, the author has
forgotten to take care of the error handler."
However, my original code was addressing the errors. It was working, except that each caller was getting it's own promise. I feel that's where I missed something.
I might be confused, but I'm thinking that the loadProjectTypes method should return the same promise/data to anyone who calls it, no matter when it's called. It should be the one true source of anything projectTypes and only make the call once, the very first time.
Any time I look for any of this (lots of purple/visited google links on these subjects), everyone is either showing chaining with contrived examples, or only using $http, or something else. I haven't found anyone doing error catching in a promise chain that uses $resource.
UPDATE: Adding my requirements for the solution. I posted them in my answer, but wanted to include them in the original post too.
Requirement 1: Allows multiple calls to the method, but only makes one API request which updates all callers with the same data.
Requirement 2: Must be able to use result of method as actual data, just as the promise spec intends. var myStuff = service.loadStuff() should actually set myStuff to be "stuff".
Requirement 3: Must allow promise chaining so that all errors in any part of the chain can be caught by a single catch at the end of the chain. As I've found in my solution, there can be more than one chain, and more than one catch, but the point is that each chain has a catch, and any "links" in the chain that break should all report their errors to their respective catch.
Isn't that always the way, as soon as you speak your problems, you come across your solution.
Requirement 1: Only make one request per method call. This is solved with the original fix to the anti-pattern. This will either always return the $resource result by either returning the cached $resource or returning and caching at the same time.
var loadProjectTypes = function(){
return shared.projectTypes || (shared.projectTypes = projectResource.getProjectTypes());
};
Requirement 2: Be able to use the service method as a promise where I can set the value of a $scope variable directly to the result of loadProjectTypes(). Using the revised method above, I can simply state $scope.theTypes = projectService.loadProjectTypes() and it'll automatically be filled with the list of types when they come in, just as the promise spec intends.
Requirement 3: Be able to chain together multiple $resource calls and have their errors be caught by a single .catch(). By using the $promise of the result of loadProjectTypes within $q.all(), I can catch any errors in any catch I want.
$q.all([
...,
projectService.loadProjectTypes().$promise,
...
])
.then(function(response){
// my project types comes in as response[n]
})
.catch(function(errResponse){
// but any errors will be caught here
});
Technically, I can put catches in different places and they'll all work the same. Anytime I have loadProjectTypes(), I can use a .catch() and my errors will be handled there. Each loader of types can handle the API being down in it's own way. This could be really good actually. A controller might get the UI to display a message and a small directive might just display something else, or nothing at all. They each can handle the bad in their own way.
My service, directive and controller look like this now:
angular.module('projects')
.factory('projectService', function(notificationService){
// an object to share data gathered by this service
var shared = {};
// $resource for projects API
var projectResource = $resource(baseApiPath + 'projects', {}, {
...,
getProjectTypes: {
method: 'GET',
url: baseApiPath + 'projects/types',
isArray: true,
transformResponse: function(response){
return JSON.parse(response).result.projectTypes;
}
},
...
});
// loads a list of project types
var loadProjectTypes = function(){
return shared.projectTypes || (shared.projectTypes = projectResource.getProjectTypes());
};
return {
shared: shared,
project: projectResource,
loadProjectTypes: loadProjectTypes
};
});
angular.module('projects')
.directive('projectPageHeader', ['projectService', function(projectService){
return {
restrict: 'E',
scope: {
active: '#',
},
templateUrl: 'src/js/apps/projects/partials/dir_projectPageHeader.html',
replace: true,
controller: function($scope){
$scope.projectService = projectService;
// sets the types to the array of types
// as given by the transformResponse
$scope.types = projectService.getProjectTypes();
// could also do a .$promise.catch here if I wanted.
// all catches will fire if get projectTypes fails.
}
};
}]);
angular.module('projects')
.controller('projectListPageController', [
'$scope','projectService',
function($scope, projectService){
// load it all up
$q.all([
projectService.loadProjectDetails($routeParams.projectId).$promise,
userService.loadUserRole('project_manager').$promise,
userService.loadUserRole('sales_representative').$promise,
projectService.loadProjectStatuses().$promise,
projectService.loadProjectTypes().$promise,
clientService.loadClients().$promise
])
.then(function(response){
// do work with any/all the responses
})
.catch(function(errResponse){
// catches any errors from any of the $promises above.
})
}]);
Since the loadProjectTypes (or any other load_____ method) saves the types within the service it comes from, I don't really need to do any storing on the controller. projectService.shared.projectTypes is universal across the entire app. The .then() method in my controller could potentially be noop if all the services were storing the results of their loads internally (which is how I like it) unless there was some view specific thing I needed to do with them. I typically only use controllers for entire pages, or $modals. Everything else is broken up into directives and most information and logic is in services.
I'm leaving the question open in case someone has a better solution. I like the one that Jack A. posted, but I feel it makes my load___ methods more verbose than they already are. Since there are a few of them with slight differences, it leads to a lot of redundant code, or complex 'smart' methods in my actual code. It definitely solves Requirement 1 and possibly 2 and 3 though.
UPDATE (GOTCHA):
So, I've been using this pattern for a few days now and it's working really exactly as I intend. It's really streamlined our process; however, I recently came upon a gotcha when using a method like loadProjectTypes in a singular context (i.e.: outside of $q.all()).
If you just use the load method like so:
// This code is just placed in your controllers init section
loadProjectTypes()
.$promise
.then(function(response){
// ... do something with response (or noop)
})
.catch(function(errResponse){
// ... do something with error
});
You will run into a situation when that controller 'refreshes'. For example, you have the code above in controllerA, you change "pages" which uses controllerB, then you go back to the first "page" and controllerA refreshes and tries to run this again. The error you get is that "there is no .then of undefined."
Inspecting this in the console, the first time loadProjectTypes() runs, it returns the response from the $resource (which includes $promise AND all the projectType data). The second time - coming back from controllerB - it will only hold the projectType data. There is no more $promise because you are not returning the result of a $resource, you returned the cached shared.projectTypes that you set after the first time. That's why we did all this, remember? I'm not sure why this goes away since that's what you saved to shared.projectTypes, but it does, and it doesn't actually matter.
return shared.projectTypes || (shared.projectTypes = projectResource.getProjectTypes());
For me, the easiest fix was to just have loadProjectTypes().$promise as the only member of a $q.all() set:
// again, this code is just placed somewhere near the top of your controller
$q.all([
loadProjectTypes().$promise
])
.then(...)
.catch(...);
In most cases, my controllers will be getting more than one thing so this would've happened eventually, but there will always be a situation where you only need to load one thing. Using a single item set in $q.all() is the only way to have no issues when using this solution. It's not that bad really, could've been worse.
I wrote something very similar to this a while ago, with a couple key differences:
I only create the promise when the data is already in the cache and return the native promise when an actual request is initiated.
I added a third state for when a request for the resource is already pending.
A simplified version of the code looks like this:
module.factory("templateService", function ($templateCache, $q, $http) {
var requests = {};
return {
getTemplate: function getTemplate(key, url) {
var data = $templateCache.get(key);
// if data already in cache, create a promise to deliver the data
if (data) {
var deferred = $q.defer();
var promise = deferred.promise;
deferred.resolve({ data: data });
return promise;
}
// else if there is an open request for the resource, return the existing promise
else if (requests[url]) {
return requests[url];
}
// else initiate a new request
else {
var req = $http.get(url);
requests[url] = req;
req.success(function (data) {
delete requests[url];
$templateCache.put(key, data);
});
return req;
}
},
};
});
(my case applies to C#, MVC, returning JSON, got jquery, angular), but I expect it applies to more than that.
I have a website where my angular/html/js calls ~7 services through Angular controllers and async-gets/displays data (weather, road conditions, etc). Some of these take longer than others (from ms to ~10s). I'd like to have a single call to my service which returns all of this data - but doesn't wait until the last call to return anything (10s).
Is there a way to make a single call, and return results as I have them and they get displayed accordingly? Do I need to have a repeating call which has a boolean like "IsMore=T" and calls the service again? (doesn't sound efficient).
Ideally, I'd like to keep a response channel open and keeping pumping results until it's done. Possible?
I'm not sure I understand completely, but I think you could just chain the response promises together, something like:
$scope.getWeatherData = function () {
return myWeatherService.get().then(function (resp) {
$scope.weatherData = resp;
});
}
$scope.getTrafficData = function () {
return myTrafficService.get().then(function (resp) {
$scope.trafficData = resp;
});
}
$scope.getWeatherData.then(getTrafficData).then(...chain others...);
This assumes that the service calls return a $http promise.
Anyway, whenever the promise comes in, the data will be on $scope, and hence the display will be updating as the promises arrive. It sounds like you might be using something like $q.all(), which would wait until all promises are resolved.
Buildilng on #reptilicus' answer:
$scope.getWeatherData = function () {
return myWeatherService.get().then(function (resp) {
$scope.weatherData = resp;
});
};
$scope.getTrafficData = function () {
return myTrafficService.get().then(function (resp) {
$scope.trafficData = resp;
});
};
$q.all([
$scope.getWeatherData(),
$scope.getTrafficData()
]).then(function () {
// do whatever's next, or nothing
});
... would request/receive both responses in parallel (if that's what you want). The relevant $scope property for each request will be populated when the related response is received, and the "do whatever's next" code will run once they are all complete.
Note, you need to inject $q to your controller constructor for this to work. :)
Edit: I just noticed that #reptilicus did mention $q.all. The difference between chaining the .thens and $q.all is that under chaining, one request wouldn't start until the previous was received....
I'm trying to figure out an elegant way to write AngularJS services without being so repetitive with the $q syntax.
Currently, I'm writing services like follows:
(function() {
function ServiceFactory($q, $timeout, $http) {
return {
getFoo: function() {
var deferred = $q.defer();
$timeout(function() {
$http.get('/the/foo/thing').then(function(response) {
if (response.isError) {
deferred.reject();
} else {
deferred.resolve(response.data.foo);
}
}, function() {
deferred.reject();
});
});
return deferred.promise;
}
};
}
angular.module('myapp').service('MyService', ['$q', '$timeout', '$http', ServiceFactory]);
}.call(this));
It works very well, buy I'm always writing down a bunch of code just to delay $http.get and expose a Promise. Sometimes I will have some extra stuff into success callback, like handling data, creating a different response object... But most of the time, is just like the code above: call $q.defer + $http.get().then... + return promise
So, I'm thinking about a way to clean up/reduce the code without affecting the clarity of what I'm doing, e.g if another developer open the file, it should not be a mystery.
As a side note, the $http service here is actually a decorator, handling server responses to give me a more structured object with things like response.isError and response.data.
Also, I have seen a similar solution in another question {1}, but this is not as same. Just returning the response of $http.get().then() will expose the entire response to controllers on response, and it is not the desired effect. Instead, when I call MyService.getFoo().then(...), I'm expecting a foo object as a response from service, fed by server via response.data.foo, or a call to errorCallback.
I've forgot to mention: my server is not RESTful, so $resource is not an option right now. My URLs are more like /thing/get/:id, /thing/do-stuff/:id.
{1} Similar question
After thinking for a while, I figured out a better way to write the services. I've done some changes to $http response, and now my implementation is returning a Promise whenever a Controller calls http.get() or whatever http methods. With this implementation, I've reduced the methods' code to two or three lines per request in most of the cases. Now I should try to use the AngularJS decorator setup.
A working example is here:
http://embed.plnkr.co/p4EHQAbE40XWXjBWqjIM/preview