future

问题 I'm new to Dart and therefore having trouble with asynchronous programming. I'm trying to loop through a list of elements (let's call them ingredients for now) and query the database for recipes which contain the ingredient. To achieve this, I have a list 'ingredientsSelectedList' and pass it over to a future which is supposed to query the Firestore Database and add the result to the 'possibleRecipes' List. The problem is, that I can't figure out how to 'await' the for loop to finish, before

问题 I'm trying to understand rational behind the statement For cases where blocking is absolutely necessary, futures can be blocked on (although it is discouraged) Idea behind ForkJoinPool is to join processes which is blocking operation, and this is main implementation of executor context for futures and actors. It should be effective for blocking joins. I wrote small benchmark and seems like old style futures(scala 2.9) are 2 times faster in this very simple scenario. @inline def futureResult[T

问题 I have a WEIRD problem with Future.get() in Java. It returns always with an InterruptedException, however the weird thing is that the cause of the Exception is null, so I cant tell who interrupted me.. It gets even worse because I check before calling get(), and the job Future has to do is already done. Here is the code responsible for the output below. f is the Future , and the callable returns a HashMap where Agent is not really relevant. Sorry if there are too many printlines, I'm just

问题 I have a WEIRD problem with Future.get() in Java. It returns always with an InterruptedException, however the weird thing is that the cause of the Exception is null, so I cant tell who interrupted me.. It gets even worse because I check before calling get(), and the job Future has to do is already done. Here is the code responsible for the output below. f is the Future , and the callable returns a HashMap where Agent is not really relevant. Sorry if there are too many printlines, I'm just

问题 I'm playing with std::variant, lambdas and std::future , and got super weird results when I tried to compose them together. Here are examples: using variant_t = std::variant< std::function<std::future<void>(int)>, std::function<void(int)> >; auto f1 = [](int) { return std::async([] { return 1; }); }; auto f2 = [](int) { return std::async([] { }); }; variant_t v1(std::move(f1)); // !!! why DOES this one compile when it SHOULDN'T? auto idx1 = v1.index(); //equals 1. WHY? variant_t v2(std::move

问题 I've found in Akka docs: When using future callbacks, such as onComplete, onSuccess, and onFailure, inside actors you need to carefully avoid closing over the containing actor’s reference, i.e. do not call methods or access mutable state on the enclosing actor from within the callback. So does it mean that i should always use future pipeTo self and then call some functions? Or i can still use callbacks with method, then how should i avoid concurrency bugs? 回答1: It means this: class

问题 I've found in Akka docs: When using future callbacks, such as onComplete, onSuccess, and onFailure, inside actors you need to carefully avoid closing over the containing actor’s reference, i.e. do not call methods or access mutable state on the enclosing actor from within the callback. So does it mean that i should always use future pipeTo self and then call some functions? Or i can still use callbacks with method, then how should i avoid concurrency bugs? 回答1: It means this: class

问题 I've found in Akka docs: When using future callbacks, such as onComplete, onSuccess, and onFailure, inside actors you need to carefully avoid closing over the containing actor’s reference, i.e. do not call methods or access mutable state on the enclosing actor from within the callback. So does it mean that i should always use future pipeTo self and then call some functions? Or i can still use callbacks with method, then how should i avoid concurrency bugs? 回答1: It means this: class

问题 How does Java's Future.get() behave in the case where it is called multiple times after the task is completed? Does it return the the same result? Or does throw an ExecutionException again and again with the same exception if the computation failed? I can not find anything in the docs about it! 回答1: You can call get() on a Future as often as you like, and it will only block if the task that produces the result has not finished yet. If the task has already finished, it will just immediately

问题 How does Java's Future.get() behave in the case where it is called multiple times after the task is completed? Does it return the the same result? Or does throw an ExecutionException again and again with the same exception if the computation failed? I can not find anything in the docs about it! 回答1: You can call get() on a Future as often as you like, and it will only block if the task that produces the result has not finished yet. If the task has already finished, it will just immediately