Eligibility:

• Return value from promise angular. It returns a single promise that will be resolved with an array of values. So the correct way doing so will be: var getReturn = function() { return "ok"; } Sep 25, 2017 · @ShinDarth You can add this function in your service and call this funcion whenever required. If the rejected value of the promise is y, then return x is equivalent to return Promise. The code looks more synchronous and, therefore, the flow and logic are more understandable. apiUrl + '/quizzes/:id/:verb', id: '@id'. If the value is a promise, that promise is returned; if the value is a thenable, Promise. public async ReadConfiguration Rather return the promise at the end of the function, then the calling function can use the promise to get the server response. Open the src/app/app. How to return Promise<Type> when value to return is of type Promise<Type | null Dec 30, 2019 · I am using Angular and Typescript to make an validation when i insert a value into a SQL database it check if the value is already in the database table. const dataToRemove = {}; dataToRemove[`teams/${key}`] = null; return this. Jul 21, 2016 · It seems to me that you've fundamentally missed a key design pattern in Javascript, which is the callback. subscribe((value) => { console. I would say do something like that: getStage(): Promise<any> {. – Mar 15, 2018 · For this input. } Explanation: lastValueFrom is used to convert an observable stream to a promise (and return the last value) forkJoin is used to subscribe to multiple observables and emit the result array after each of them have completed. nextlink': string; } I would like to avoid using nested promises in my component so I am using Angular 6. Here's an excerpt from the class: Jul 27, 2018 · 20. function isOnline() {. That's not how it works with promises. 8,844 6 76 90. Step 2 : Return an ‘async’ method in the component : Here is the typescript code: Notice the words ‘async’ and ‘await’. Jun 27, 2017 · It returns the result of a then() call, which, so far as I understand, is a Promise. filterData;" with just the data I need from promise as interface Data[] Another component : receiving the results, here I would like it be the interface Data[] Dec 31, 2014 · If the resolved value of the promise is y, then return x is equivalent to return Promise. They are pretty brilliant and allow you to write async code that reads synchronous. find(); Jul 13, 2021 · return value in subscribe in angular. This function flattens nested layers of promise Sep 22, 2017 · 2. Mar 17, 2016 · Since the function is not asynchronous, there's no need for a promise. ts file and add the following imports: import { Component } from '@angular/core'; import { Observable, of } from 'rxjs'; import { delay } from 'rxjs/operators'; Next, define two asyncPromise and asyncObservable variables as follows: Nov 19, 2019 · Since the Http service returns observables, which are kind of like super-promises, you can just use an observable operator to combine the two. How to return the promise then()/catch() result to the function containing the promise? 1. Sep 22, 2014 · How to use Promise to return value from assync Angular function into calling method? 0. then(val => self. It returns the value in the future ("promises" to return a value) when it's available. But async functions still only return Promise objects. They represent asynchronous values (that may not be populated yet), so you can't just cast an asynchronous value to a synchronous one. By adding (<jasmine. The tech stack that I'm using is Angular, Typescript and Express. I've spent the whole day trying to figuring this out but I failed. returnValue(Promise. May 26, 2022 · How to use firstValueFrom & lastValueFrom to convert an Observable to a Promise in Angular 13+ applications. then on a promise and return something from it - we get a promise for the processed value. Successfully call the Angular GetData() function on page load and I've traced to confirm that Home/DataRefresh is returning data in the correct format. Feb 18, 2016 · As I understood your case, you seem to be stuck on returning something. find(); return promise; //Or return query. props() iterates an object to find all properties that have promises as values and uses Promise. Its async and the calling code has moved on by the time the promise return is called. Angular would the apply the changed value and rearrange the DOM-Elements. – . If it is not a function, it is internally replaced with an identity function ( (x Mar 2, 2017 · ) "When RxJs converts an Observable to a Promise, it creates a Promise that will yield the last value from the observable. If we return another promise we'll get amazing things, but let's hold our horses. setTimeout(() => { const data TypeScript. I think it is because the Promise resolve is asynchronous. but when I want to get the value its still a promise. Additional check if callback was specified should be added. pipe(select(getSelectedMemberType(), {id: memberId})) This will put the current value of the Observable inside memberId. You can't directly get a value out of a promise. This also solves the this problem that your code has: service = {. And when it becomes available (or not), one of two callbacks passed to then() methods gets triggered. I want to ask that how can we return a promise from the subscribe function. pipe( map(x => { return this. data which is a promise object ? My service is, listing. map is used to "enrich" the initial items. When we call . This class is used to create new promises and handle the results of asynchronous operations. You can't get a return value from the function you pass to setTimeout. Ask Question Asked 2 years, 10 months ago. * onwards. ts : Dec 11, 2016 · 17. Simplified code: this. public showDialog(theNickname: string): any { it still doesn't Feb 19, 2019 · So the retrieveAllTeams returns a Promise of type RetrieveMultipleResponse. setCurrent(quiz); }); return result; }, And the quizResource in QuizService looks like this: AppSettings. getTranscriptValue() { return "dummy" }, getConfidenceValue() { return "another dummy" } fetchTransValues() {. The implementation of the function it's ok. Mar 13, 2018 · And I do know a lot about Angular. This tutorial is part of the Tour of Heroes series that teaches you the basics of Angular development. then(function() {. eth. Mar 22, 2020 · Below are the steps of how to use them : Step 1: Write the template code . Feb 25, 2016 · How to simply return a pre-resolved promise in AngularJS. Oct 20, 2015 · 10. Whatever you want to do with the value you get, you need to do it from the function you pass to setTimeout. May 26, 2020 · First, let me demonstrate that returning a "raw" value and a Promise value from an async / await function both yield the same result. Dec 6, 2018 · And later on i need to call questions. Make a note of some of the following in the code given Sep 10, 2019 · 0. C) When x is a Promise that is pending: return x will return a pending Promise, and it will be evaluated on the subsequent then. Still, if you want some laziness, then you must try RxJS observables. TypeScript. return this. Feb 26, 2017 · JavaScript is single-threaded. subscribe((v) => {. var promise = new Promise((resolve, reject) => { }); We pass to Promise an inner function that takes two arguments (resolve, reject). myService. var promise = query. The function that called setTimeout ( x in your example) will finish executing and return before the function you pass to setTimeout is even called. Return promise value from Dec 6, 2023 · A function to asynchronously execute when this promise becomes fulfilled. Hope this helps someone simplify the process. It also notifies via the return value of the notifyCallback method. all(). lastValueFrom now takes a configuration parameter as its second parameter, and you can specify a default value that will be emitted if the observable is empty: await rxjs. I can get the data to return inside of the getData() function however, the data is not passed on in the return statement, I just get an empty array in ngOnInit(); Nov 7, 2018 · The problem is, if I put the return in the then() it will say: [ts] A function whose declared type is neither 'void' nor 'any' must return a value. The interface looks like that: export interface RetrieveMultipleResponse { value: Entity[]; '@odata. To create a new promise in Angular, you can use the Promise constructor as below. subscribe() then takes the value that Observable holds and assigns it to this. take(1) . The code snipped in the given example is correct. And, to do this, I'm going to use ts-node to run some TypeScript from my command-line: return( "Raw value" ); return( Promise. modalService. The code given below works for Angular 4. NET CORE API, if the value is already in the table database server will return true. profile = val); I set a constant of self retaining the this global object otherwise the promise itself is referred to, rather than the parent. map() to iterate and await the whole array of May 18, 2021 · Angular promise return. That single promise is resolved when all of the input promises are resolved. function doSomething(success) {. I would like to update the view scope based on the result (success/fail) but of course the http request used by the service is asynchronous so the return value is not immediately available and comes up undefined in the controller. It can only return a pending promise which is resolved at a later time or an empty reference that is later populated with data from the server. js. answered Nov 8, 2022 at 13:32. get return promises. and you really would not need to have catch and return false unless you need to really track the return value since dialog already resolves/rejects the promise based on cancel or Ok, i. If I change. com"; let data = "so much data, very impresive"; return Promise. Typescript generic Promise return T or void. The closest you can get to that is using async/await. A safer way to manage this is to use async functions in these places because they consistently use promises: async onClick() {. As I understand the functionality of switchMap(), it takes whatever it is given and makes a new Observable out of it. This is a generic code using angular reactive form. Aug 20, 2021 · I always have a utility function for this which uses the RxJS operator take(1): let val: T. Each value of the array corresponds to the promise at the same index/key in the promises array. @Input() callback: () => Promise<null>; there is no guarantee that it's assigned to proper value. console. The response is just this: true Apr 18, 2019 · Adding a Promise won't solve the issue, it will just add more code that it's really unneeded, since the result can be binded to angular property directly without the need of a Promise or anything. Jul 6, 2017 · As I said before, the returned values from the successCallback and errorCallback are considered values resolved for the promise. Aug 26, 2021 · 8. But now that I'm trying to build my own application I'm running into a bit of a problem. As you have used async, use await. io. – Nov 22, 2016 · Here we return a new Promise. then(result => { return result; }) is totally pointless; it was already a promise of that result value. In your Service, create this function. . After obtaining the API key, navigate back to your project in the Angular IDE and create a TypeScript src file in the app folder Jul 10, 2017 · Promise. modalRef = this. // Perform asynchronous operation. content. pipe(take(1)). removeTeam(key: string) {. Jan 10, 2019 · You don't need to return a string, you can return Promise<string> or Observable<string> and chain the async pipe to resolve the value. I have to apply a decryption on the body of the return of a request via Interceptor, however the method of decrypting is asynchronous and returns a promise. You use a . Even if you return a false value or nothing, the value will be considered resolved. const bl = await web3. It needs to be returned because the function calling it will need the JWT of the User. – jfriend00. I. In this section, you will learn the usage of Promise with Angular HttpClient service. retrieving data from a server) first. Apr 19, 2017 · Of course, it is not returning the string value as it is being returned as a promise. (It is still promises under the hood, just unboxing of them). g. findMembersInTeam(key) May 16, 2018 · How to return value when using pipe and map, like in this scenario: return this. Jul 11, 2018 · Alerting "alert(this. Angular promise return. Sep 14, 2016 · service. Nov 8, 2022 · console. Also, method used to return string value form service is not allowing to write method without final return statement as mentioned in code below [right now I've added two return statement from Promise, which doesn't seems correct design to me, but without it i'm getting compilation error], and both return statements gets executed at different Jan 15, 2018 · Promise & Angular HttpClient Service. push(new DropdownQuestion(element)) Dec 6, 2023 · The Promise. action. show(DemoModalComponent); this. The issue is caused by a tiny difference, in local storage the "get" methd simply returns a value, but Ionic's storage "get" method returns a promise. ts : Jul 11, 2018 · Alerting "alert(this. Here user enters a ‘name’ value in a textbox and clicks on ‘Search’ button . Let's see how we can solve the above issue with promises. resolve(true); } async function Main() {. const self = this; this. I'm working on an auth service that has only a login and a logout for now. resolve([server, data]); } on the other side, you can use the destructuring expression for ES2015 to get the individual values. Promises are always keen to be invoked. You can't receive a plain string from a promise - a promise is async so you have to handle it async. Return value with asynchronous functions in Typescript. Feb 15, 2018 · I'm testing a function that receives a value from a promise, and concat this value (string) to an url. navigate promise with a returnvalue as otherwise it will ent into a Promise. In ECMAScript 2017 a new feature to handle asynchronous requests was introduced—async functions and the await keyword. then() function. navigate). As silicon Soul mentioned you need definately mock the router. resolve(y). }, You cannot return a value from a promise . hero. This way the program will wait on the await line until the Promise is resolved and then continue. EDIT: For ES2017 If your one of the lucky souls who gets to use ES2017 then you can use the new await/async keywords. subscribe it there. IF sdkDB returns an Observable, import rxjs/add/operator/mergeMap and use flatMap or mergeMap (flatMap is just an alias of mergeMap) instead of subscribe. You should also look into using the async / await syntax, which simplifies working with promises, and the async pipe in Angular allows you This method returns a new promise which is resolved or rejected via the return value of the successCallback, errorCallback (unless that value is a promise, in which case it is resolved with the value which is resolved in that promise using promise chaining). the main thing is that how can i directly return something from inside promise success ? Although can you plz share code snippet of converting to Observable only ? it might help to solve the issue. first sample: because this is a async call, second console. A function can not return data that is not available. it will still tell me this : A function whose declared type is neither 'void' nor 'any' must return a value (about getCompte, it can be fixed by adding return 'test' at the end, but it'll still return it anyways :/ – Oct 21, 2019 · From a service constructor, I want to call 2 HttpClient. Source. – I'm building an ASP. Any suggestions? Feb 15, 2022 · 1. It's just that the design chosen by the OP is wrong, because the task of checking if a value changes cannot be done with a timeout and, in angular When the promise resolves and the UI element renders I can then click on that UI element. component. In js there isn't a method like "wait for promise". The value that the promise was fulfilled with. timestamp; } So, further you can use it function like: const time = await latestTime(); May 4, 2013 · However, while this gets rid of the digest cycle error, you still cannot call the function from the view--I suspect Angular is treating the return value (the promise itself) as a truthy value, rather than binding to the promise's resolved value. When the constructor is completed, the 2 get requests have to be already completed. this. toPromise(); Nov 2, 2019 · thanks, but since all this code is in the . openConfirmDialogBox() { this. A promise may be in one of 4 possible states: fulfilled, rejected, pending or settled. Note that HttpClient is the recommended way for communicating with remote APIs from Angular 5. log('output', output); //no data. With promises. But I think the good approach for this case will be to return a Promise. var data = 1; // blah blah blah, something happens. NET MVC application with an Angular front-end. profile$. Its return value becomes the fulfillment value of the promise returned by then(). 2. How can I return the string value? It is being called from an Angular function on the html. You're already returning an observable from that method, why not use from again? – jonrsharpe May 20, 2023 · Angular provides a built-in implementation of promises through the Promise class. Mar 17, 2022 · How about using plain rxjs for the job instead of mixing promises in there? When using angular, Angular 2: How to fetch data and return single values? 1. Hi Rob, not sure why you would want to mock a call that a mock makes to another service surely you would want to test that when testing that function. getBlock('latest'); return bl. – Alexander Staroselsky Jun 29, 2016 · isValid = (value: any) => { return this. edited Apr 15, 2022 at 12:21. public showDialog(theNickname: string): string { to. For example, the more modern Ajax replacement fetch or jQuery's $. So switchMap() receives a Promise back. resolve() static method "resolves" a given value to a Promise. You can also convert the Observable into a Promise and await . resolve()); the unit test should be ok. I am simply redoing a formerly written angular app in Ionic but the issue started ever since I decided to use the Ionic "storage" instead of the "localStorage". store. So basically, you should make calls like this: Mar 1, 2018 · Click on Create credentials to create credentials for your app. log won't wait for subscribe to finish before it executes. The idea is not to create and return the promise from inside the callback, but to create it in the outside function (where you can return it) and only resolve the promise from the callback: myFunction ():Promise<any> { return new Promise (resolve => { libapi. The only downside is you won't be able to use async/await with it. const myVal = await utility. Dec 2, 2017 · Last example is returning a promise anyway, it suppose to return value instead a promise, I did await response. Aug 8, 2017 · 4. for more info read documentation to read more about Observables check this if you are new to Rxjs check this. " – => return promise; <= instead here I would like to "return this. Resolved promise: A nice short way to return a static value when stubbing out http service calls. return Promise. then. Aug 28, 2018 · Return value from a promise in Angular. Async/Await works on top of promises and makes asynchronous code easier to read and write. user = user; //in between I fill some fields for the user. then or . I don't want to use a timeout function. Usually the Promise won't resolve instantly, but will perform an async task (e. Using firstValueFrom & lastValueFrom using then & catch syntax. Jun 18, 2021 · So there a couple things wrong here but I don't think the promise is one of them. firstValueFrom code example: Aug 19, 2020 · Let's now see an example of using the async pipe with both an observable and promise. Mar 22, 2021 · Async/Await. Return value will be `Promise, so in your case it will be: async function latestTime(): Promise<some primitive> {. get asynchronously. Instead of returning a value from the function, you pass in some code to execute when the function is good and ready. let server = "myserver. Returning from a promise callback (or resolve function) will only pass data to the next . return false; Sep 22, 2014 · How to use Promise to return value from assync Angular function into calling method? 0. Dec 4, 2021 · I'm having trouble making a function that returns the data "array" that I want to consume using a Promise. modalRef. e below blocks wont be needed. reject(y). checkValue(value); } Otherwise Angular calls the method with this of the component, not the consumer of the component. getApi(). log(value) // here value passed on clicking ok will be printed in console. const promise = new Promise((resolve, reject) => {. Since we have an array of objects, we use Promise. and. This combines your observable streams. Jan 11, 2017 · yes, ionic 2 storage returns promise of successful retrieval of data from storage and then angular 2 http post method returns Observable. text() and returns another promise, I want the value alone, and this does not work at all. As I said. May 12, 2018 · How to return a promise from subscribe in angular 5. then(url => {. A promise represents an operation that hasn't completed yet. You can make it look different using async/await, but it is just syntactic sugar. Jan 26, 2018 · How to return data as Promise type in Angular 2? Using this function I need to return data as promise type: private getStudyPeriods(): Promise<CurrentPeriod> { let data = []; return data;// here } I tried last variant like this: Jul 6, 2018 · As @jfriend00 mentions in your comment discussions that this is a dupe of similar questions, whenever using asynchronous functions (Promise, Observable) you should bubble up the asynchronicity back to the call and . Resolve your promise with the trans and confidence results, and capture those when the promise resolves. The promise cannot 3. The final unit test should look like: 18. o. Simply use combineLatest() to combine the two return values as an array, just like with Promise. You will also learn how to use observables, promises, and RxJS to handle asynchronous data flows. service. AngularJS getting out a return value from a Promise. httpService. you can only pass one value, but it can be an array with multiples values within, as example: function step1(){. A promise is a JavaScript/TypeScript object that may produce a value at some point in time. resolve( "Promise value" ) ); Jun 24, 2017 · I recently started learning Angular (4) and followed the tutorials of Angular. Promises simplify deferred and asynchronous computations. See the provided answer. Your function signature says that you have the option to return one of three types, canActivate(): boolean | Observable<boolean> | Promise<boolean> But you only ever return a boolean, so really you could re-write this as just, canActivate(): boolean May 2, 2019 · 2. isGreaterThanZero starts with the value of "false" and gets changed to "true" if, and only if, the expected return value is received. someEvent(). RxJS 7 comes with a built-in function firstValueFrom which takes an Observable as its first argument and returns a Promise. it's simply not possible, you can't play with the stuff you've bought before it has been delivered, not even if you have a delivery notification; or the guy at the store promised you Apr 25, 2024 · It combines multiple promises in Angular into a single promise. Spy>routerStub. }) return val. So the returned response in the errorCallback will solve the promise instead reject it. I get a response from an ASP . 4. Learn how to use Angular HTTP to communicate with a remote server and perform CRUD operations in this tutorial. return true; }, function() {. then(response=> {}. Jan 16, 2017 · I have a service that (when it's all said and done) updates a value on the database. 3 and Angular 5 apps. In my controller code where I handle the click I would like to act on the value of the promise. get<ServerStatus >(url). push(new DropdownQuestion(element)); for this one, i am unable to get the value in newValue and so the questions. lastValueFrom(observableThing, {defaultValue: "oh no - empty!"}) answered Apr 21, 2022 at 23:29. someValue; }) ) but the value is never returned since never subscrubed to the event, if i use it like this: Jul 14, 2018 · async function will return Promise anyway. Aug 19, 2016 at 6:24. At this point in my angular code I already know that the promise is resolved. log("Async Work Complete"); resolve(); }, 1000); }); We usually return this promise from a function, like so: Oct 22, 2019 · A callback function can also be attached to the Promise’s fulfilled or rejected state to reveal the purpose of success or rejection. then() handler on the promise to get access to the value. Small hint regarding performance (though not tested): if this method is large and the instance-count of the component is high, then you should factor out the bigger parts of the Apr 2, 2018 · Observable runs when you subscribe to it and what return from subscription is always a subscription object like setInterval. var promise = new Promise((resolve, reject) => { setTimeout(() => { . push(new DropdownQuestion(element)) is giving empty values so after storing the value in newValue, i need to call this one, questions. . fetchInfo(); For this to work you have to add async to the function that contains this line: async function funcName(). 54. Since we are defining the function we can call these arguments whatever we want but the convention is to call them resolve and reject. May 10, 2020 · You cannot have such a function return a boolean, because by the time the function itself ends, you don't have the information to return true or false. resolve() will call the then() method with two callbacks it prepared; otherwise the returned promise will be fulfilled with the value. The body of the Promise calls the resolve method when it is done (in this case that is instantly), triggering the Promise to resolve and execute all then methods chained to the Promise. Apr 29, 2017 · Utilising the then() method to return the promise, I populate a variable free of the $ notation. reject(). The function is called with the following arguments: value. Check out my detailed article on handling HTTP requests with RxJS Observables in Angular 2+. 0. Thus the promise will not resolve until the underlying observable completes. show(); Jul 5, 2018 · I may not get the concept right about Promise() in Angular, but how should I modify below code so that checkExistence() can return a boolean? public checkExistence(value: string): boolean{ var e Nov 2, 2020 · I recommend you read up on how to work with promises in JS and Angular. all() to await all those promises and it returns a new object with all the original properties, but the promises replaced by the resolved values. A promise can be: Sep 29, 2023 · Here’s a basic example of using Promises in Angular: function fetchData() { return new Promise((resolve, reject) => { // Simulate an asynchronous operation. data)" gives me [object Promise], so my question is how to fetch the data from this. spinnerService. val = v. James Moore. I would use the async and await keywords. Angular httpclient will always return an observable (RXjs) , promise is not available in Angular, it was available in AngularJs, you need to subscribe to the observable. callnetwork (arg1, callback (data) { resolve (data); }); }); } or simply. mz pz eb hq sv db qb qy ym yn