async-await

问题 I have an async/await function of which I want to use the result to conditionally render a jsx component in my React native application. This a class method that returns a promise. The method has async declared. The problem is I want to use the result of this to conditionally render some jsx. const hasEdit = await perms.has('/page', 'edit'); return ( <div> { hasEdit && <Button icon='pencil' text='EDIT' onTouchTap={ () => { props.onEdit(); } } /> } </div> ) This returns: A valid React element

问题 Below is my API endpoint for creating an event in my application. I'm also using Cloudinary API for uploading my images and storing the returned URL into my database. app.post('/event', (req, res) => { try { if (req.body.images.length > 0) { // Creating new Event instance const event = new Event({ title: req.body.title, images: [], }); // Looping over every image coming in the request object from frontend req.body.images.forEach((img) => { const base64Data = img.content.split(',')[1]; //

问题 What should be expected from Task.WaitAll(t1, t2) , when t2 's execution syncs with t1 , but t1 throws an exception before the point it syncs to t2 ? In this case, it's obvious that t2 will never finish. However since t1 throws an exception, I expected Task.WaitAll(t1,t2) to return with aggregated exception indicating one of the task fails. However this is not the case. It turns out that Task.WaitAll hangs waiting forever. I can argue for this behavior that Task.WaitAll does what it claims to

问题 I've never used the async-await syntax but I do often need to make HTTP/S requests and parse responses while awaiting future responses. To accomplish this task, I currently use the ThreadPoolExecutor class which execute the calls asynchronously anyways; effectively I'm achieving (I believe) the same result I would get with more lines of code to use async-await . Operating under the assumption that my current implementations work asynchronously, I am wondering how the async-await

问题 I ran into a problem that I cannot seem to solve, I'm guessing I'm missing some points in terms of async behaviour. The task is relatively simple: A wallet with money in different currencies needs to be transformed into a single currency. I want to get the exchange rate from following API: https://free.currencyconverterapi.com/api/v5/convert?q=${from}_${to}&compact=y With ${from} being the starting currency and ${to} the target currency. I store the different currencies in an object called

问题 I'm implementing network layer of my application, that is using an asynchronous JSON-RPC protocol. In order to communicate with the server, i'd like to make a method that will send a proper request, wait until the server sends response, and return it. Everything with use of async/await keywords. Here's simplified sample code: string response; Task<string> SendRequest(string methodName, string methodParams) { string request = generateRequest(methodName, methodParams); await Send(request); //

问题 I have a websocket server (python 3.x) taking requests where each is a url variable. It runs just fine except it only executes each request in serial, after one another. While the function is running it also blocks the client(s) trying to connect. Non-blocking is what i want! Asyncronous multiprocessed threading of both websocket and subprocess function. The ability to set the number of cores to use. This is not obligatory though. Here's what i've got: ANSWER (illustration and asyncio

问题 I have a repository method in a ASP WebApi site public async Task<IEnumerable<Animal>> GetAnimals(List<long> herdIds) { using (var sqlConnection = new OracleConnection(Connectionstring)) { await sqlConnection.OpenAsync(); var sql = GetCommonSqlQuery(herdIds, true); var result = await sqlConnection.QueryAsync<Prop1, Prop2, Prop3, Prop1>( sql, (a, g, b) => { a.Prop2 = g; a.Prop3= b; return a; }); return result; } } I use that with Task<IEnumerable<Animal>> animalsTask = animalsRepository

问题 I have a private ConcurrentDictionary that is a simple lookup table of some DB keys. I'm trying to leverage the ConcurrentDictionary so that it will only do one call to the db when 2+ requests to the same line of code, are made at the same time. (Which is why i'm using a ConcurrentDictionary .) How can I do this please? This is what I was trying to do .. but I think it's storing the Task in the dictionary ... not the result of the task.... private readonly ConcurrentDictionary<string, Task

问题 I've been reading the source code of UserManager.cs and I've stepped into the following block: public virtual Task<TUser> GetUserAsync(ClaimsPrincipal principal) { if (principal == null) { throw new ArgumentNullException(nameof(principal)); } var id = GetUserId(principal); return id == null ? Task.FromResult<TUser>(null) : FindByIdAsync(id); } I've been very curious if there is a reason why the above is not like this: public virtual async Task<TUser> GetUserAsync(ClaimsPrincipal principal) {