I have over 200 Future functions request rest api.
ex)
Future fetchSomething(jsonData) async {
var dio = Dio();
try {
var response = await dio.post(
"serverurl",
data: FormData.fromMap(jsonData),
options:Options(contentType: Headers.formUrlEncodedContentType));
return response.data;
}
catch (e) {
throw Exception(e);
}
}
and I want the app pop modal that explain what error it is when the error occur
since I have over 200 Future functions, It's going to be hassle to put exception logic to every Future function.
Is there a way to put common logic easily?
Thank you.
Related
Im having issues with my code and since I'm new at using Flutter, I have no clue on how to fix it. I was trying to fix the http.get(string) and I kind of did, but now I'm having issues with then(()).
void submitForm(FeedbackForm feedbackForm) async {
try {
await http.get(Uri.parse(URL + feedbackForm.toParams()).then((response)) {
callback(convert.jsonDecode(response.body['status']));
});
} catch (e) {
print(e);
}
}
}
It seems you got a parenthesis missplaced:
await http.get(...).then((response) => callback(...))
The them allows you to use the result of the previous Future, as soon as it becomes available. If you find it confusing you can declare one variable at a time.
final response = await http.get(...);
// Check if response was as expected
await callback();
Looking for help here guys. I have 2 Futures that populate data in sqflite. I need one (_insertInitialData()) to finish first before calling the second one (_insertAdditionalData()). I have done it this way, but it's not working. It first does the re-recreation of the DB as expected, then both _insertInitialData() and _insertAdditionalData() not in the order I expected. I have tried .whenComplete and calling here _insertAdditionalData() and also have tried different ways that I think should work but nothing.
This is just something I'm doing for fun but still I'd like to know what I'm doing wrong.
TIA
Future<void> _insertAdditionalData() async{}
void populateDB() {
try {
final localDB = LocalDatabase.instance;
Future.wait([localDB.dropDB(recreateDB: true)]).then((_){
print('DB recreated!');
Future.wait([_insertInitialData()]).then((_) {
print('_insertInitialData done');
Future.wait([_insertAdditionalData()]).then((_){
print('_insertAdditionalData done');
});
});
});
} catch (ex) {
print('There was a problem in populateDB(): $ex');
}
}```
Using await makes things a lot easier to read and will block execution of later lines until the action has finished.
Future<void> populateDB() async {
final localDB = LocalDatabase.instance;
await localDB.dropDB(recreateDB: true);
print('DB recreated!');
await _insertInitialData();
print('_insertInitialData done');
await _insertAdditionalData();
print('_insertAdditionalData done');
}
You can try using only one future statement, and follows it with multiple "then". This makes sure the first "then" will be completed before the second "then" is executed. I assume your localDB.dropDB(recreateDB: true) function is asynchronous.
Future<void> _insertAdditionalData() async{}
void populateDB() {
try {
final localDB = LocalDatabase.instance;
localDB.dropDB(recreateDB: true).then((_){
print('DB recreated!');
}).then((_) {
_insertInitialData();
print('_insertInitialData done');
}).then(() {
_insertAdditionalData();
print('_insertAdditionalData done');
});
} catch (ex) {
print('There was a problem in populateDB(): $ex');
}
}
Cool. Thanks for your comments. I replaced all of those Future.wait for async/await even in my internal methods that insert into the DB and it's all good!!! (executing in the sequence I need)
Just learning Dart/Flutter for fun and I love it.
I am trying to implement a Dio interceptor so I will be able to use it with my code.
I will be using this interceptor in many places. So I thought it would make sense to put it into a class or an interface whichever is best and just extend or implement it my subclasses.
I have this so far:
class AppInterceptor {
Dio dio = Dio();
AppInterceptor() {
dio.interceptors
.add(InterceptorsWrapper(onRequest: (Options options) async {
var token = await getAuthorizationToken();
options.headers["Authorization"] = 'Bearer $token';
return options;
}, onResponse: (Response response) {
// Finally, the string is parsed into a JSON object.
//print(response.toString());
return response;
}, onError: (DioError e) {
print('somthing went wrong');
// Do something with response error
return e; //continue
}));
}
}
How do I use this in a subclass to make an http call?
I tried something like this when trying to do my http call:
Response response = await AppInterceptor.dio.post(Global.functionsUrl+'/auth/linkuseraccount/', data: {'hey': 'hello'});
print(response);
It fails each time with Unhandled Exception: DioError [DioErrorType.RESPONSE]: Http status error [403]
From my backend, I can tell that it fails because the interceptor didn't pass in the authentication header.
How should I go about this?
getData() async {
http.Response response = await http.get('https://www.example.com/);
print(response.body);
}
The above function works to get the HTML code of a page but it fails in some cases. The function is sometimes never completed and it waits forever to get response( For example, if the app is opened while internet is off and even when its turned on, it never connects). In such situations is there any way to retry ?
I tried the http retry package but it gives me 15+ errors.
Example code for how this could be done:
import 'package:http/http.dart' as http;
import 'dart:convert';
Future<List> loadData() async {
bool loadRemoteDatatSucceed = false;
var data;
try {
http.Response response = await http.post("https://www.example.com",
body: <String, String>{"username": "test"});
data = json.decode(response.body);
if (data.containsKey("success")) {
loadRemoteDatatSucceed = true;
}
} catch (e) {
if (loadRemoteDatatSucceed == false) retryFuture(loadData, 2000);
}
return data;
}
retryFuture(future, delay) {
Future.delayed(Duration(milliseconds: delay), () {
future();
});
}
You can use RetryPolicy from http package to retry your connection, just create your own class and inherit form RetryPolicy and override these function like the following example, then create a Client using HttpClientWithInterceptor.build and add your custom retryPolicy as a parameter, this will retry your request for a number of times until a condition is met, if not, it'll just stop retrying.
import 'package:http/http.dart';
class MyRetryPolicy extends RetryPolicy {
final url = 'https://www.example.com/';
#override
// how many times you want to retry your request.
int maxRetryAttempts = 5;
#override
Future<bool> shouldAttemptRetryOnResponse(ResponseData response) async {
//You can check if you got your response after certain timeout,
//or if you want to retry your request based on the status code,
//usually this is used for refreshing your expired token but you can check for what ever you want
//your should write a condition here so it won't execute this code on every request
//for example if(response == null)
// a very basic solution is that you can check
// for internet connection, for example
try {
final result = await InternetAddress.lookup('google.com');
if (result.isNotEmpty && result[0].rawAddress.isNotEmpty) {
return true;
}
return false;
} on SocketException catch (_) {
return false;
}
}
}
then create and use a client to make your requests.
it will automatically retry the request if the condition you wrote is met.
Client client = HttpClientWithInterceptor.build(
retryPolicy: ExpiredTokenRetryPolicy(),
);
final response = await client.get('https://www.example.com/);
there is also a package to check for internet connection if that your problem, see connectivity
You can use try-catch blocks inside async functions like you would in synchronous code. Perhaps you'd be able to add some sort of error handling mechanism in the function, and retry the function on error? Here's some documentation on that one.
Example from the docs:
try {
var order = await getUserOrder();
print('Awaiting user order...');
} catch (err) {
print('Caught error: $err');
}
You can also catch specific Exceptions, per this github issue.
doLogin(String username, String password) async {
try {
var user = await api.login(username, password);
_view.onLoginSuccess(user);
} on Exception catch(error) {
_view.onLoginError(error.toString());
}
}
EDIT: This may also help.
While we're at it, look here for a function that reattempts an async operation however many times you need.
I am trying to make a simple request to backend using rxDart. But the problem I face is that when I get a http error such as 404, onError is not called, however, it is possible to extract it in onData.
I have a little experience with RxJava + retrofit and there it works as expected, when there is a response with error http status code onError is called and can be handled appropriately.
1. What am I doing wrong, or is it intended behavior?.
Object sendProfileData() {
Stream<Response> stream = onboardingRepository.createUser(User(name: 'name', surname: 'surname', lat: 1.0, lng: 2.0));
stream.listen((response) {
print(response.statusCode);
setAttributes();
}, onError: (e) {
print(e);
});
}
OnboardingRepository.dart:
class OnboardingRepository {
Observable<Response> createUser(User user) {
return Observable.fromFuture(TMApi.createUser(user));
}
}
TMApi.dart:
class TMApi {
static Future<http.Response> createUser(User user) async {
String url = '$baseUrl/create_user';
return await http.post(url, body: json.encode(user.toJson()));
}
}
What would be the best way to handle the event in the View? There should be an error displayed if error occurs, otherwise it should open a new screen. sendProfileData() method will return an Object, based on that I am going to perform actions in the view, but that doesn't sound like a very elegant solution...
Any suggestions on architecture are welcome :)
the http library in dart works a bit different than Retrofit.
The Future returned by http.post only throws an exception when there is an io error (socket error, no internet).
Server responses like 404 are reflected in the http.Response.
I created a simple convenience method that might help you:
void throwIfNoSuccess(http.Response response) {
if(response.statusCode < 200 || response.statusCode > 299) {
print('http error!');
print(response.body);
throw new HttpException(response);
}
}
class HttpException implements Exception {
HttpException(this.response);
http.Response response;
}
How to use:
import 'dart:convert';
import 'package:http/http.dart' as http;
Future<UserProfile> getUserProfile(String userId) async {
final url = 'https://example.com/api/users/$userId';
final response = await http.get(url);
throwIfNoSuccess(response);
final jsonBody = json.decode(response.body);
return UserProfile.fromJson(jsonBody);
}