dart:async is a Dart library for asynchronous operations.
dart:async is a Dart library for asynchronous operations.
It supports streams, futures and allows to create timers.
Questions tagged [dart-async]
314 questions
95
votes
2 answers
How do you get the current stacktrace in Dart for a Completer.CompleteException(exception, stackTrace);
If some code returns a future and determines that the future should return "Error" or "Exception" how can a stack trace be passed to Completer.completeException(exception, stackTrace);
adam-singer
- 4,489
- 4
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- 25
81
votes
13 answers
is there any way to cancel a dart Future?
In a Dart UI, I have a button submit to launch a long async request. The submit handler returns a Future. Next, the button submit is replaced by a button cancel to allow the cancellation of the whole operation. In the cancel handler, I would like to…
Serge Tahé
- 1,869
- 2
- 19
- 20
69
votes
10 answers
Flutter - setState not updating inner Stateful Widget
Basically I am trying to make an app whose content will be updated with an async function that takes information from a website, but when I do try to set the new state, it doesn't reload the new content. If I debug the app, it shows that the current…
Jesús Martín
- 1,293
- 2
- 11
- 11
56
votes
6 answers
41
votes
2 answers
How do I do the equivalent of setTimeout + clearTimeout in Dart?
I'm porting some JavaScript to Dart. I have code that uses window.setTimeout to run a callback after a period of time. In some situations, that callback gets canceled via window.clearTimeout.
What is the equivalent of this in Dart? I can use new…
Danny Tuppeny
- 40,147
- 24
- 151
- 275
26
votes
2 answers
DART: syntax of future then
I don´t understand the syntax of the then() clause.
1. myFuture(6).then( (erg) => print(erg) )
What´s (erg) => expr syntactically?
I thougt it could be a function, but
then( callHandler2(erg)
doesn´t work, Error:
"Multiple markers at this line
-…
mica
- 3,898
- 4
- 34
- 62
25
votes
2 answers
Dart/Flutter - "yield" inside a callback function
I need to yield a list for a function; however, I want to yield the list from within a callback function, which itself is inside the main function - this results in the yield statement not executing for the main function, but rather for the callback…
Marcus Bornman
- 375
- 3
- 7
25
votes
4 answers
Flutter BLoC pattern - How can I navigate to another screen after a stream event?
My question is about navigation used with the BLoC pattern.
In my LoginScreen widget I have a button that adds an event into the EventSink of the bloc. The bloc calls the API and authenticates the user.
Where in the LoginScreen Widget do I have to…
Sebastian
- 3,666
- 2
- 19
- 32
20
votes
7 answers
How to test an exception from a future
Continuing from yesterday question, how would I test that a async method throws an exception.
main(){
test( "test2", () async {
expect( await throws(), throwsException);
});
}
Future throws () async {
throw new…
richard
- 2,887
- 5
- 26
- 36
18
votes
1 answer
The purpose of function `runZoned` of 'dart:async'
There is a special function runZoned provided by dart:async. The document is here: https://api.dartlang.org/docs/channels/stable/latest/dart_async.html#runZoned
I'm not sure what's the purpose of this function, when will we need it, and how to use…
Freewind
- 193,756
- 157
- 432
- 708
17
votes
3 answers
Completer and Future in dart?
Future readData() {
var completer = new Completer();
print("querying");
pool.query('select p.id, p.name, p.age, t.name, t.species '
'from people p '
'left join pets t on t.owner_id = p.id').then((result) {
…
IBRIT
- 385
- 1
- 3
- 13
16
votes
2 answers
Getting values from Future instances
My data is something like this:
{
"five": {
"group": {
"one": {
"order": 2
},
"six": {
"order": 1
}
},
"name": "Filbert",
"skill": "databases"
},
"four": {
"group": {
"three":…
Hesh
- 413
- 1
- 3
- 11
13
votes
1 answer
What's the difference between returning void vs returning Future?
Is there a difference between an async method that returns void, and one that returns Future? It seems that both are valid in Dart:
void main() async {
await myVoid();
await myFutureVoid();
}
void myVoid() async {
// Do…
Magnus
- 17,157
- 19
- 104
- 189
12
votes
6 answers
How do I create a blank Future in Dart + how do I return a future currently in progress?
I'm trying to create a server-side Dart class that performs various data-related tasks. All of these tasks rely on the database having been first initialized. The problem is that the init of the database happens asynchronously (returns a Future). I…
Greg Sherman
- 1,084
- 1
- 11
- 22
12
votes
4 answers
Dart - how to mock a method that returns a future
I have a class that defines a method that returns a Future. The Future contains a list of class that also return a future.
class User{
Future> albums(){
};
}
class Album{
Future> photos(){
…
richard
- 2,887
- 5
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- 36