Dart newbie here, I'm currently learning about asynchronous execution in Dart. I'm a bit irritated about how concurrency works in Dart, take the following scenario from their codelab:
void printOrderMessage () async {
try {
var order = await fetchUserOrder();
print('Awaiting user order...');
print(order);
} catch (err) {
print('Caught error: $err');
}
}
Future<String> fetchUserOrder() {
// Imagine that this function is more complex.
var str = Future.delayed(Duration(seconds: 4), () => throw 'Cannot locate user order');
return str;
}
Future<void> main() async {
await printOrderMessage();
}
In this case, the asynchronous operation is fetching the the user order from say a DB. Now because of Dart's await / async mechanism, every function that is related to the async operation is required to have a Future<> return type and must be tagged with async.
This feels clunky ... Imagine if some value deep in my function chain is being calculated asynchronously, would I really need to always return a future? Is there some other construct to synchronize code in Dart than await? Or have I misunderstood the concept?
If callers need to be able to wait for your asynchronous operation to finish, then your asynchronous function must return a Future that can be awaited. This is contagious; if callers of those callers need to be able to wait, then they too need to have Futures to wait upon.
If callers should not wait, then you can have a "fire-and-forget" function that does not need to return a Future:
Future<void> foo() {
// ...
}
// Does not need to return a Future. Consequently, callers cannot
// directly determine when `foo` completes.
void bar() {
foo();
}