I'm finding it difficult making sense of all the differing blogs and examples out there on how to use a promise correctly in angular, so would appreciate some clarification from someone please.
Is using a callback passed in to the service get method to set the controller variable like this wrong?
In the Session service:
self.getSessions = function(callback) {
$http.get(self.urls.sessionsList).then(
function (response) {
callback(response.data);
},
function (response) {
// failure
}
);
};
from this controller:
.controller('SessionsController', ['Session', function(Session) {
var self = this;
self.sessions = [];
Session.getSessions(function(data) {
self.sessions = data;
});
}])
Q) Is using a callback passed in to the service get method to set the controller >>variable like this wrong?.
No, it is not wrong, but you can use the power of the promise and change your code to be something like below, where you can chain to the "then" method :
self.getSessions = function() {
return $http.get(self.urls.sessionsList);
}
and change your controller code to be:
.controller('SessionsController', ['Session', function(Session) {
var self = this;
self.sessions = [];
Session.getSessions().then(function(response) {
self.sessions = response.data;
});
}]);
Then, you can see that the caller can chain the to "then" and do more and more functionality,...
hope that helps.
Use Deffered promise is bad thing since es6 promise is released
Related
I have been working with wrapping my head around the "angularjs" way of thinking (Angular 1) and I have a relatively ok grasp as I work my way through a small personal project. I am at a bit of a roadblock, not because I cannot get it to work, but I would like to know what the proper way to set up the data in my application.
The basic situation is this:
I have 3 json files:
categories.json
products.json
vendors.json
These hold the data (which I will fetch from a database later but am simplifying for now).
I basically need to load the data from all three of these files so that I can form a variable holding all "Products" (which is a JS class I declared separately).
I started off by storing the data inside one controller (relevant code below):
myApp.controller('productListController', ['$scope', '$http', '$q', function ($scope, $http, $q) {
var promises = [];
promises.push(getCategories($http));
promises.push(getVendors($http));
promises.push(getProducts($http));
$q.all(promises).then(function (response) {
//categories = response[0];
//vendors = response[1];
//products = response[2];
$scope.products = createProductList(response);
$scope.vendors = response[1].data;
$scope.vendorChecked = getCheckedVendors($scope.vendors);
})
This worked fine but I realized that I need this data in other views, which led me to try to move this code into a service.
The problem I had when doing this is that I do not know of a way for the controller to know that the service is done fetching the data so that I can then save it in the ProductListController $scope.
I would need to have a way to for example:
myApp.service('ProductService', ['$http', '$q', function ($http, $q) {
self = this;
var promises = [];
promises.push(getCategories($http));
promises.push(getVendors($http));
promises.push(getProducts($http));
$q.all(promises).then(function (response) {
//These three I would like to update in ProductListController
//when it is done.
self.products = createProductList(response);
self.vendors = response[1].data;
self.vendorChecked = getCheckedVendors(self.vendors);
})
Is this the correct approach to take? If so, how can I let the controller know that the service is done fetching the data and save for example:
$scope.products = ProductService.products;
$scope.vendors = ProductService.vendors;
$scope.categories = ProductService.categories;
Is this even the correct approach? Another approach I thought of was to use a factory instead of a service. Then I had another problem because I had for example:
return {
getProducts: function() {
//http get request code in here
return promise
},
getVendors: function() {
//http get request code in here
return promise
},
getCategories: function() {
//http get request code in here
return promise
},
getAllData: function () {
//in here I want to use the three promises in the 3 functions above
//but I am not able to call them from here. If I was able to do that
//then I could call this method from ProductListController and get the
//data that way.
}
I am sorry if this is long but I wanted to describe the different things I tried. I know I can make it work but I want to learn the right way, or a couple of right ways.
It is better to always return promise:
var promises = [];
promises.push(getCategories($http));
promises.push(getVendors($http));
promises.push(getProducts($http));
return $q.all(promises)
If you also not satisfied that in each controller you should call createProductList,getCheckedVendors - consider putting this tranforms to $http transformResponce https://docs.angularjs.org/api/ng/service/$http.
Or you can create your own promise. (Using $q.defer https://docs.angularjs.org/api/ng/service/$q).
Using servie or factory actually doesnt matter. This is factory:
var factory = {};
factory.getProducts: function() {
return promise
}
factory.getCategories: function() {
return promise
}
factory.getVendors: function() {
return promise
}
factory.getAllData: function () {
var promises = [];
promises.push(factory.getProducts());
promises.push(factory.getCategories());
promises.push(factory.getVendors());
return $q.all(promises)
}
return factory;
And in controler you just have:
MyFactory.getAllData().then(...)
This might be a nooby question but I still haven't been able to get my head around promises and specifically how to write code with them. (I've read several articles but most of them are abstract and I simply haven't written enough to have a clear picture)
I've got an AngujlarJS application that gets data through a http request to another server which sends a promise at first. I've been able to retrieve the response from the promise and use it in my app. However because my code is poorly written. It executes other code before the promise is resolved leading to problems. It starts loading the page before it has the data.
what i have is:
var userTotals = *http request which returns a promise
$scope.data = userTotals.$object
//code that does someting with $scope.data
What i need is (I think)
var userTotals = *http request which returns a promise
$scope.data = userTotals.$object.
beforethisresolves(function{
show fancy loading icon or something })
.whenthis resolves(function{
//code that does someting with $scope.data
}
however I can't get the syntax correct.
This is what it looks like in general:
var promise = $http.post('/url');
console.log('Request started');
promise.then(function(result) {
console.log('Success');
console.log(result);
}, function() {
console.log('Failure');
});
In fact, $q AngularJS documentation helped me a good deal to get my head around promises concept.
Hope this helps!
var successCallback = function(){//...};
var errorCallback = function(){//...};
$http
.post('url', data)
.success(successCallback)
.error(errorCallback);
//OR
$http
.post('url', data)
.then(successCallback, errorCallback);
Assuming that you're using Bootstrap modal you can do the following:
function openModalWithProgressIndicator(deferred) {
const progressModal = $uibModal.open({
templateUrl: 'templates/modals/progress.html',
backdrop: 'static'
});
return deferred.then(function (value) {
return value;
}).finally(function () {
progressModal.close();
});
}
The deferred argument passed to this function is a promise. That said you can now do the following:
const deferred = $http.post('http://somewhere/data', {foo: 'bar'});
openModalWithProgressIndicator(deferred)
.then(function (httpResponse) {
// do sth with httpResponse.data
}).catch(function (error) {
// do sth with error
});
So the main point to note is the finally callback that's always executed.
Recently it has become possible to use angularjs within google apps script via the iframe sandbox mode.
My problem comes when trying to communicate with the server (gapps spreadsheet) and receiving asynchronous data in return.
The implementation for receiving data from the server is to use a function with a callback function like so:
google.script.run.withSuccessHandler(dataGatheringFunction).getServerData();
getServerData() would be a function that resides server-side that would return some data, usually from the accompanying spreadsheet. My question is how to use the callback function within the parameters of AngularJS. A typical $http function could be placed in a provider, and the scope value could be populated after then.() returns. I could also invoke $q. But how would I deal with the necessity of google's callback?
Here's a simplified version of what I'm messing with so far:
app.factory("myFactory", function($q){
function ssData(){
var TssData = function(z){
return z;
}
google.script.run.withSuccessHandler(TssData).getServerData();
var deferred = $q.defer();
var d = deferred.resolve(TssData)
console.log("DP: " + deferred.promise);
return deferred.promise;
}
return ssData();
})
Then in the controller resolve the server call similar to this:
myFactory.then(set some variables here with the return data)
My question is simply - How do I deal with that callback function in the provider?
The script throws no errors, but does not return the data from the server. I could use the old $timeout trick to retrieve the data, but there should be a better way.
You only need to $apply the output from the server function:
google.script.run.withSuccessHandler(function(data) {
$scope.$apply(function () {
$scope.data = data;
});
}).withFailureHandler(errorHandler).serverFunction();
Maybe the most elegant solution that makes sure the google.script.run callbacks are registered automatically in the AngularJS digest cycle would be to use the $q constructor to promisify the google callbacks. So, using your example above:
app.factory('myFactory', ['$q', function ($q){
return {ssData: ssData};
function ssData(){
var TssData = function(z){
return z;
};
var NoData = function(error) {
// Error Handling Here
};
return $q(function(resolve, reject) {
google.script.run
.withSuccessHandler(resolve)
.withFailureHandler(reject)
.getServerData();
}).then(TssData).catch(NoData);
}
}]);
Then in your controller you can call myFactory.ssData()
Since I don't know exactly what TssData is doing I included it here but note that this simply returns another promise in this context which you will still have to handle in your controller:
myFactory.ssData().then(function(response) {
// Set data to the scope or whatever you want
});
Alternately, you could expose TssData by adding it to the factory's functions if it is doing some kind of data transformation. If it is truly just returning the response, you could refactor the code and omit TssData and NoData and handle the promise entirely in the controller:
app.factory('myFactory', ['$q', function ($q){
return {ssData: ssData};
function ssData(){
return $q(function(resolve, reject) {
google.script.run
.withSuccessHandler(resolve)
.withFailureHandler(reject)
.getServerData();
});
}
}]);
app.controller('myController', ['myFactory', function(myFactory) {
var vm = this;
myFactory.ssData()
.then(function(response) {
vm.myData = response;
}).catch(function(error) {
// Handle Any Errors
});
}]);
An excellent article about promises (in Angular and otherwise) is here: http://pouchdb.com/2015/05/18/we-have-a-problem-with-promises.html
This guy seems to be pulling data from a GSheet into angular quite happily without having to do anything fancy.
function gotData(res) {
$scope.validUser = res.validUser;
var data = angular.copy(res.data), obj, i=0;
Object.keys(data).forEach(function(sh) {
obj = {title: sh, checked: {}, showFilters: false, search: {}, sort: {index: 0, reverse: false}, currentPage: 0, checkedAll: true, showBtns: true, searchAll: ''};
obj.heading = data[sh].shift();
obj.list = data[sh];
obj.heading.forEach(function(s,i) {
obj.checked[i] = true;
});
$scope.sheets.push(obj);
});
$scope.sheets.sort(function(a,b) {
return a.title > b.title ? 1 : -1;
});
$scope.gotData = true;
$scope.$apply();
}
google.script.run.withSuccessHandler(gotData).withFailureHandler($scope.gotError).getData();
My solution was to get rid of the $q, promise scenario all together. I used $rootScope.$broadcast to update scope variables from the server.
Link to spreadsheet with script.
Two Important Notes:
1. My goal is to AVOID using $scope in this case since it's my understanding that impedes the new "controller as" syntax.
2. My problem is likely a variable scope issue and so perhaps just clarifying the proper JS way might solve the problem.
Nevermind the exports, I'm working with browserify in my workflow.
I have this working code:
exports.IntroCtrl = function($scope, $http) {
$scope.introData = [];
$http.get('data/intro.json')
.success(function(res){
$scope.introData = res;
});
};
That ideally I'd like to work as something like this, for the sake of using the "controller as" syntax.
exports.IntroCtrl = function($http) {
this.introData = [];
$http.get('data/intro.json')
.success(function(res){
introData = res;
});
};
The problem is that the $http service seems to be executing before my initial this.introData declaration since I get a variable not defined error.
If tell this.introData = $http.get… then it returns an array of 5 objects that I can't access and intro.json only contains 4.
Thanks for any guidance/help.
First of all create a service for the http call. It is very convenient way to get the callback in the controller and then assign your controller as variables. Here is the factory for you:
Factory
app.factory('getDataService',function ($http) {
return {
getData:function(callback){
$http.get('data/intro.json')
.success(callback)
});
}
}
});
In your controller you get inject the getDataService and bind the data like this:
Controller:
app.controller('testController',['getDataService',function(testDataService){
this.introData = [];
testDataService.getData(function(data){
this.introData = data;
});
}]);
Here you need to bind the introData of the controller function.
You have to remember this variable that reference the controller instance, and use it later in the success callback like this:
exports.IntroCtrl = function($http) {
this.introData = [];
var ctrl = this; // remember 'this', the controller instance, to use in the success callback below
$http.get('data/intro.json')
.success(function (res) {
ctrl.introData = res;
});
};
Hope this helps.
I am using some data which is from a RESTful service in multiple pages.
So I am using angular factories for that. So, I required to get the data once from the server, and everytime I am getting the data with that defined service. Just like a global variables. Here is the sample:
var myApp = angular.module('myservices', []);
myApp.factory('myService', function($http) {
$http({method:"GET", url:"/my/url"}).success(function(result){
return result;
});
});
In my controller I am using this service as:
function myFunction($scope, myService) {
$scope.data = myService;
console.log("data.name"+$scope.data.name);
}
Its working fine for me as per my requirements.
But the problem here is, when I reloaded in my webpage the service will gets called again and requests for server. If in between some other function executes which is dependent on the "defined service", It's giving the error like "something" is undefined. So I want to wait in my script till the service is loaded. How can I do that? Is there anyway do that in angularjs?
You should use promises for async operations where you don't know when it will be completed. A promise "represents an operation that hasn't completed yet, but is expected in the future." (https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Promise)
An example implementation would be like:
myApp.factory('myService', function($http) {
var getData = function() {
// Angular $http() and then() both return promises themselves
return $http({method:"GET", url:"/my/url"}).then(function(result){
// What we return here is the data that will be accessible
// to us after the promise resolves
return result.data;
});
};
return { getData: getData };
});
function myFunction($scope, myService) {
var myDataPromise = myService.getData();
myDataPromise.then(function(result) {
// this is only run after getData() resolves
$scope.data = result;
console.log("data.name"+$scope.data.name);
});
}
Edit: Regarding Sujoys comment that
What do I need to do so that myFuction() call won't return till .then() function finishes execution.
function myFunction($scope, myService) {
var myDataPromise = myService.getData();
myDataPromise.then(function(result) {
$scope.data = result;
console.log("data.name"+$scope.data.name);
});
console.log("This will get printed before data.name inside then. And I don't want that.");
}
Well, let's suppose the call to getData() took 10 seconds to complete. If the function didn't return anything in that time, it would effectively become normal synchronous code and would hang the browser until it completed.
With the promise returning instantly though, the browser is free to continue on with other code in the meantime. Once the promise resolves/fails, the then() call is triggered. So it makes much more sense this way, even if it might make the flow of your code a bit more complex (complexity is a common problem of async/parallel programming in general after all!)
for people new to this you can also use a callback for example:
In your service:
.factory('DataHandler',function ($http){
var GetRandomArtists = function(data, callback){
$http.post(URL, data).success(function (response) {
callback(response);
});
}
})
In your controller:
DataHandler.GetRandomArtists(3, function(response){
$scope.data.random_artists = response;
});
I was having the same problem and none if these worked for me. Here is what did work though...
app.factory('myService', function($http) {
var data = function (value) {
return $http.get(value);
}
return { data: data }
});
and then the function that uses it is...
vm.search = function(value) {
var recieved_data = myService.data(value);
recieved_data.then(
function(fulfillment){
vm.tags = fulfillment.data;
}, function(){
console.log("Server did not send tag data.");
});
};
The service isn't that necessary but I think its a good practise for extensibility. Most of what you will need for one will for any other, especially when using APIs. Anyway I hope this was helpful.
FYI, this is using Angularfire so it may vary a bit for a different service or other use but should solve the same isse $http has. I had this same issue only solution that fit for me the best was to combine all services/factories into a single promise on the scope. On each route/view that needed these services/etc to be loaded I put any functions that require loaded data inside the controller function i.e. myfunct() and the main app.js on run after auth i put
myservice.$loaded().then(function() {$rootScope.myservice = myservice;});
and in the view I just did
ng-if="myservice" ng-init="somevar=myfunct()"
in the first/parent view element/wrapper so the controller can run everything inside
myfunct()
without worrying about async promises/order/queue issues. I hope that helps someone with the same issues I had.