>
> Le 18 sept. 2017 à 18:07, Pierre Habouzit <[email protected]> a écrit :
>
>
> -Pierre
>
>> On Sep 18, 2017, at 2:04 AM, Trevör Anne Denise
>> <[email protected] <mailto:[email protected]>> wrote:
>>
>>>
>>> Le 18 sept. 2017 à 07:57, Pierre Habouzit <[email protected]
>>> <mailto:[email protected]>> a écrit :
>>>
>>>> On Sep 17, 2017, at 3:52 AM, Trevör ANNE DENISE via swift-evolution
>>>> <[email protected] <mailto:[email protected]>> wrote:
>>>>
>>>> Hello everyone,
>>>>
>>>> I have a few questions about async await in Swift.
>>>>
>>>> Say that you have :
>>>>
>>>> func foo() async {
>>>> print("Hey")
>>>> await bar()
>>>> print("How are you ?")
>>>> }
>>>>
>>>> First of all, am I right to say that :
>>>> 1) If the bar function wasn't an async function, the thread would be
>>>> blocked until bar returns, at this point print("How are you ?") would be
>>>> executed and its only after that that the function calling foo() would get
>>>> back "control"
>>>
>>> I don't think you can quite call await without marking foo() as async (?).
>>
>>
>> Yes, that's what I meant, case one would call foo() without await if it
>> wasn't async.
>>
>>
>>>
>>>> 2) Here (with async bar function), if bar() takes some time to execute,
>>>
>>> Not quite, `await bar()` is afaict syntactic sugar for:
>>>
>>> bar {
>>> printf("How are you ?");
>>> }
>>>
>>> Where bar used to take a closure before, the compiler is just making it for
>>> you. bar itself will be marked async and will handle its asynchronous
>>> nature e.g. using dispatch or something else entirely.
>>> This has nothing to do with "time".
>>
>>
>> If it's just syntactic sugar then how does this solve this issue mentioned
>> in the concurrency manifesto ?
>> "Beyond being syntactically inconvenient, completion handlers are
>> problematic because their syntax suggests that they will be called on the
>> current queue, but that is not always the case. For example, one of the top
>> recommendations on Stack Overflow is to implement your own custom async
>> operations with code like this (Objective-C syntax):"
>
> "where" things run is not addressed by async/await afaict, but Actors or any
> library-level usage of it.
>
So since async await don't have any impact on where things are executed, what
would happen concretely with this code ?
func slowFunction(_ input: [Int]) async -> [Int] {
var results = [Int]()
for element in input {
results += [someLongComputation(with: element)]
}
return results
}
beginAsync {
await slowFunction(manyElements)
}
I didn't specified anything about which queue/thread runs this code, so what
would happen ? Would beginAsync block until slowFunction completes ?
Trevör
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