Here's what I have going:
import 'whatwg-fetch';
function fetchVehicle(id) {
return dispatch => {
return dispatch({
type: 'FETCH_VEHICLE',
payload: fetch(`http://swapi.co/api/vehicles/${id}/`)
.then(status)
.then(res => res.json())
.catch(error => {
throw(error);
})
});
};
}
function status(res) {
if (!res.ok) {
return Promise.reject()
}
return res;
}
EDIT: The promise doesn't get rejected, that's what I'm trying to figure out.
I'm using this fetch polyfill in Redux with redux-promise-middleware.
Fetch promises only reject with a TypeError when a network error occurs. Since 4xx and 5xx responses aren't network errors, there's nothing to catch. You'll need to throw an error yourself to use Promise#catch.
A fetch Response conveniently supplies an ok , which tells you whether the request succeeded. Something like this should do the trick:
fetch(url).then((response) => {
if (response.ok) {
return response.json();
}
throw new Error('Something went wrong');
})
.then((responseJson) => {
// Do something with the response
})
.catch((error) => {
console.log(error)
});
The following login with username and password example shows how to:
Check response.ok
reject if not OK, instead of throw an error
Further process any error hints from server, e.g. validation issues
login() {
const url = "https://example.com/api/users/login";
const headers = {
Accept: "application/json",
"Content-Type": "application/json",
};
fetch(url, {
method: "POST",
headers,
body: JSON.stringify({
email: this.username,
password: this.password,
}),
})
.then((response) => {
// 1. check response.ok
if (response.ok) {
return response.json();
}
return Promise.reject(response); // 2. reject instead of throw
})
.then((json) => {
// all good, token is ready
this.store.commit("token", json.access_token);
})
.catch((response) => {
console.log(response.status, response.statusText);
// 3. get error messages, if any
response.json().then((json: any) => {
console.log(json);
})
});
},
Thanks for the help everyone, rejecting the promise in .catch() solved my issue:
export function fetchVehicle(id) {
return dispatch => {
return dispatch({
type: 'FETCH_VEHICLE',
payload: fetch(`http://swapi.co/api/vehicles/${id}/`)
.then(status)
.then(res => res.json())
.catch(error => {
return Promise.reject()
})
});
};
}
function status(res) {
if (!res.ok) {
throw new Error(res.statusText);
}
return res;
}
For me,
fny answers really got it all. since fetch is not throwing error, we need to throw/handle the error ourselves.
Posting my solution with async/await. I think it's more strait forward and readable
Solution 1: Not throwing an error, handle the error ourselves
async _fetch(request) {
const fetchResult = await fetch(request); //Making the req
const result = await fetchResult.json(); // parsing the response
if (fetchResult.ok) {
return result; // return success object
}
const responseError = {
type: 'Error',
message: result.message || 'Something went wrong',
data: result.data || '',
code: result.code || '',
};
const error = new Error();
error.info = responseError;
return (error);
}
Here if we getting an error, we are building an error object, plain JS object and returning it, the con is that we need to handle it outside.
How to use:
const userSaved = await apiCall(data); // calling fetch
if (userSaved instanceof Error) {
debug.log('Failed saving user', userSaved); // handle error
return;
}
debug.log('Success saving user', userSaved); // handle success
Solution 2: Throwing an error, using try/catch
async _fetch(request) {
const fetchResult = await fetch(request);
const result = await fetchResult.json();
if (fetchResult.ok) {
return result;
}
const responseError = {
type: 'Error',
message: result.message || 'Something went wrong',
data: result.data || '',
code: result.code || '',
};
let error = new Error();
error = { ...error, ...responseError };
throw (error);
}
Here we are throwing and error that we created, since Error ctor approve only string, Im creating the plain Error js object, and the use will be:
try {
const userSaved = await apiCall(data); // calling fetch
debug.log('Success saving user', userSaved); // handle success
} catch (e) {
debug.log('Failed saving user', userSaved); // handle error
}
Solution 3: Using customer error
async _fetch(request) {
const fetchResult = await fetch(request);
const result = await fetchResult.json();
if (fetchResult.ok) {
return result;
}
throw new ClassError(result.message, result.data, result.code);
}
And:
class ClassError extends Error {
constructor(message = 'Something went wrong', data = '', code = '') {
super();
this.message = message;
this.data = data;
this.code = code;
}
}
Hope it helped.
2021 TypeScript Answer
What I do is write a fetch wrapper that takes a generic and if the response is ok it will auto .json() and type assert the result, otherwise the wrapper throws the response
export const fetcher = async <T>(input: RequestInfo, init?: RequestInit) => {
const response = await fetch(input, init);
if (!response.ok) {
throw response;
}
return response.json() as Promise<T>;
};
and then I'll catch errors and check if they are an instanceof Response. That way TypeScript knows that error has Response properties such as status statusText body headers etc. and I can apply a custom message for each 4xx 5xx status code.
try {
return await fetcher<LoginResponse>("http://localhost:8080/login", {
method: "POST",
headers: {
Accept: "application/json",
"Content-Type": "application/json",
},
body: JSON.stringify({ email: "user#example.com", password: "passw0rd" }),
});
} catch (error) {
if (error instanceof Response) {
switch (error.status) {
case 401:
throw new Error("Invalid login credentials");
/* ... */
default:
throw new Error(`Unknown server error occured: ${error.statusText}`);
}
}
throw new Error(`Something went wrong: ${error.message || error}`);
}
and if something like a network error occurs it can be caught outside of the instanceof Response check with a more generic message i.e.
throw new Error(`Something went wrong: ${error.message || error}`);
The answer by #fny (the accepted answer) didn't work for me. The throw new Error() wasn't getting picked up by the .catch. My solution was to wrap the fetch with a function that builds a new promise:
function my_fetch(url, args) {
return new Promise((resolve, reject) => {
fetch(url, args)
.then((response) => {
response.text().then((body) => {
if (response.ok) {
resolve(body)
} else {
reject(body)
}
})
})
.catch((error) => { reject(error) })
})
}
Now every error and non-ok return will be picked up by the .catch method:
my_fetch(url, args)
.then((response) => {
// Do something with the response
})
.catch((error) => {
// Do something with the error
})
function handleErrors(response) {
if (!response.ok) {
throw Error(response.statusText);
}
return response;
}
fetch("https://example.com/api/users")
.then(handleErrors)
.then(response => console.log("ok") )
.catch(error => console.log(error) );
I wasn't satisfied with any of the suggested solutions, so I played a bit with Fetch API to find a way to handle both success responses and error responses.
Plan was to get {status: XXX, message: 'a message'} format as a result in both cases.
Note: Success response can contain an empty body. In that case we fallback and use Response.status and Response.statusText to populate resulting response object.
fetch(url)
.then(handleResponse)
.then((responseJson) => {
// Do something with the response
})
.catch((error) => {
console.log(error)
});
export const handleResponse = (res) => {
if (!res.ok) {
return res
.text()
.then(result => JSON.parse(result))
.then(result => Promise.reject({ status: result.status, message: result.message }));
}
return res
.json()
.then(result => Promise.resolve(result))
.catch(() => Promise.resolve({ status: res.status, message: res.statusText }));
};
I just checked the status of the response object:
$promise.then( function successCallback(response) {
console.log(response);
if (response.status === 200) { ... }
});
Hope this helps for me throw Error is not working
function handleErrors(response) {
if (!response.ok) {
return new Promise((resolve, reject) => {
setTimeout(() => {
reject({
status: response.status,
statusText: response.statusText,
});
}, 0);
});
}
return response.json();
}
function clickHandler(event) {
const textInput = input.value;
let output;
fetch(`${URL}${encodeURI(textInput)}`)
.then(handleErrors)
.then((json) => {
output = json.contents.translated;
console.log(output);
outputDiv.innerHTML = "<p>" + output + "</p>";
})
.catch((error) => alert(error.statusText));
}
Another (shorter) version that resonates with most answers:
fetch(url)
.then(response => response.ok ? response.json() : Promise.reject(response))
.then(json => doStuff(json)) //all good
//next line is optional
.catch(response => handleError(response)) //handle error
I have an existing async function:
async doJSONGetRequest(getUrl, accessToken) {
return new Promise(function(resolve, reject) {
const reqHeaders = {
'Content-Type': 'application/json',
'Authorization': `Bearer ${accessToken}`,
};
console.info('url = ' + getUrl);
request.get({
url: getUrl,
headers: reqHeaders,
}, function(err, response) {
if (err) return reject(err);
try {
// console.debug(`response = ${response.body}`);
const parsed = JSON.parse(response.body);
return resolve(parsed);
} catch (err) {
return reject(err);
}
});
});
}
}
I'm trying to test it with Jasmine(v4).
Of course, I don't want this thing to actually make an HTTP request, so I tried rigging up a spy on the 'request' package's 'get' function in the 'beforeAll' section:
describe('RAPIDAPIService', function() {
beforeAll(async function() {
spyOn(request, 'get')
.and
.callFake(async (parameters) => {
if (parameters.url === 'http://localhost/api/getSomething') {
const rsp = {};
rsp.body = 'good stuff';
return rsp;
} else if (parameters.url === 'http://localhost/api/whoops') {
return new Error('401 not found');
} else {
return null;
}
});
});
it('doJSONGetRequest should run successfully', async () => {
expect(api.doJSONGetRequest).toBeDefined();
const res = await api.doJSONGetRequest('http://localhost/api/getSomething', '12345678');
expect(data).toEqual('good stuff');
});
it('doJSONGetRequest should resolve errors properly', async () => {
expect(api.doJSONGetRequest).toBeDefined();
const res = await api.doJSONGetRequest('http://localhost/api/whoops', '12345678');
const expectedError = new Error('401 not found');
expect(res).toEqual(expectedError);
});
Console log statements seem to indicate that I'm actually getting past / returning something from my "await" calls in the "it" tests. But the spies are actually working / detecting that the url's have been called.
(Note that I'm not including here other tests in the same file that do not make asynchronous calls and ARE working... just so you know that there's no problem accessing the actual "api" library and its functions.)
These two tests keep failing with "Error: Timeout - Async function did not complete within 5000ms". And like I said, it seems like they're not returning back to the tests from their calls to the doJSONGetRequest function.
Any thoughts?
Thanks!
I am thinking the issue is the mocking. request.get seems to take two parameters and I am thinking you need to call the 2nd parameter (callback function) once you are done so the resolve can be called.
Try this:
spyOn(request, 'get')
.and
// add callbackFunction as 2nd argument
.callFake((parameters, callbackFunction) => {
if (parameters.url === 'http://localhost/api/getSomething') {
const rsp = {};
rsp.body = 'good stuff';
callbackFunction(null, rsp);
} else if (parameters.url === 'http://localhost/api/whoops') {
callbackFunction({ error: '401 not found' }, {});
} else {
callbackFunction(null, null);
}
});
I want to block the function from returning value before promise resolves. And, pushheaders returns an promise obj instead of just value,
i just want pushheaders to return token which fetched from the firebase
import firebase from 'firebase';
let promise1 = new Promise((resolve, reject) => {
firebase.auth().currentUser.getIdToken().then(token => {
resolve(token);
}).catch(err => {
reject(err)
});
});
export function pushHeaders (ct) {
let b = await promise1.then(data => data);
let headerz = {
headers: {
Authorization: 'Bearer ' + b,
}
}
ct ? (headerz.headers['Content-Type'] = ct) : null;
return headerz;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.6.2/react.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/15.6.2/react-dom.min.js"></script>
There is no way to synchronize promises so with await your function needs to be async:
export async function pushHeaders(ct) {
const token = await promise1; // no need for a noop
const headers = {
headers: {
Authorization: `Bearer ${token}`,
...(ct ? { 'Content-Type': ct } : {}), // ECMAScript2018
},
};
return headers;
}
This also means that it returns a promise and not headers directly. To get the actual result you either need to use then or use asycn/await again on the callee.
I see you are using await, which is a typescript keyword, which is only allowed when you mark your function with Async, try that
export async function pushHeaders (ct) {
I have method in some service:
public approveTokenExpiration(): Observable<any> {
let header = new Headers();
header.append('Authorization', this.getTokenHeaderValue());
let options = new RequestOptions({headers: header});
return this.http.get(Constants.oauthLoginEndPointUrl, options)
.map(res => {
return res;
})
.catch(err => {
return refreshToken()
.subscribe(res => {
return res;
});
});
}
refresh token method:
public refreshToken(): Observable<any> {
let refreshToken = localStorage.getItem(Constants.REFRESH_TOKEN);
let refreshEndPointUrl = Constants.oauthLoginEndPointUrl + "?grant_type=refresh_token&client_id=" +
Constants.clientId + "&client_secret=" + Constants.clientSecret + "&refresh_token=" + refreshToken;
this.http
.post(refreshEndPointUrl, {})
.map(res => {
this.setAuthLocalStorageItems(res);
this.removeAuthLocalStorageItems();
return res;
});
}
And subscription:
request(url: string|Request, options?: RequestOptionsArgs): Observable<Response> {
this.customOptions = options;
return this.authService.approveTokenExpiration()
.subscribe(
res => {
this.addAuthHeader();
return super.request(url, this.customOptions);
},
err => {
this.authService.refreshToken();
this.addAuthHeader();
return super.request(url, this.customOptions);
});
}
I'm getting following error:
ERROR in [at-loader] ./src/app/auth/intercept/auth.interceptor.ts:18:5
TS2322: Type 'Subscription' is not assignable to type 'Observable'.
Property '_isScalar' is missing in type 'Subscription'.
And check pls if everything is okay with my RxJs handling;
There are a couple of problems with your code. The specific problem you raised is caused by this part:
request(url: string|Request, options?: RequestOptionsArgs): Observable<Response> {
this.customOptions = options;
return this.authService.approveTokenExpiration()
.subscribe(... // <- this will return a Subscription
Notice that you define the request function to return a result of type Observable<Response>. However, your return statement is returning ...subscribe(), which is a Subscription. If you want to return an observable, don't call .subscribe(). Just return what you get from approveTokenExpiration()
You're on the right track. The request function should return an Observable. It is the calling code (your component) that should call .subscribe() on that Observable because it is at that point the request will be triggered.
My provider makes available an API for an http.get request:
join(){
let headers = new Headers();
headers.append('Content-Type', 'application/json');
headers.append('x-access-token',this.getToken());
return Observable.create(observer =>{
this.http.get('/localhost/chat/'+this.room,{headers : headers})
.map(res => res.json())
.subscribe(
data=>{
observer.next(data);
},
(err) =>{
observer.error(err);
}
);
})
}
My page.ts just use this API cyclically:
join(){
this.myProvider.join().subscribe(
(data)=>{
if(data.success){
... /* doing smt */ ....
this.join();
}else{
this.message=data.message;
//TBD sleep....
//this.join();
}
},
(err) => {
this.message="Connectivity with server Lost...";
});
}
My question is: I would like to write a function in page.ts in order to stop this cycle.
How can I kill a pending get request?
A solution that doesn't work was
I tried to keep a pointer to the observable object in my page.ts:
export class Page {
...
join_channel: any;
join(){
this.join_channel = this.myProvider.join().subscribe(
(data)=>{
...
this.join();
...
Then I by calling the this.join_channel.unsubscribe() I wanted to close the request, so in my case:
ionViewWillLeave() {
this.join_channel.unsubscribe();
delete this;
}
But even by unsubscribing, the get request is still there pending; so when I try to enter again in my page, a new join() can't receive a http.get response at the first step, because the answer will be used before for the previous request which is still pending.
Use timeout from rxjs
this.http.get(API)
.timeout(2000)
.map(res => res.json()).subscribe((data) => {
return data;
},
(err) => {
return err;
}
);
Don't forget to import import 'rxjs/add/operator/timeout';
If you are using angular 6 you have to use
pipe(timeout(2000))
this.http.get(API)
.pipe(timeout(2000))
.map(res => res.json()).subscribe((data) => {
return data;
},
(err) => {
return err;
}
);