async-await | 易学教程

Are you there, asynchronously written value?

阅读更多关于 Are you there, asynchronously written value?

问题 The last couple of days I've been reading about async/await. Yesterday I found this video on Channel 9 what made wonder about some things. Please consider the slide below. Aside from the issues Lucian Wischik addresses, I wondered about variable assignment. Say we changed the async void into async Task , and added await before the SendData call. This enables us to get the stream, assign the variable m_GetResponse , wait for two seconds and print it. But what happens to the variable? It could

Are you there, asynchronously written value?

阅读更多关于 Are you there, asynchronously written value?

How to get returned value without await opeartor

阅读更多关于 How to get returned value without await opeartor

问题 I need to get the returned value without await operator(in below sample I need to get the "hello world" in var y without await operator). Because one method is referred to a lot of places.But my requirement is that method is executed at asynchronously for particular operations. None other time it is enough to be executed as synchronously. If I put await in all referred places that method needs to change as async and also referred methods need to change as async and await. Is there any

Testing async HTTP-based function with Jasmine and await: Expected one matching request for criteria “…”, found none

阅读更多关于 Testing async HTTP-based function with Jasmine and await: Expected one matching request for criteria “…”, found none

问题 WHAT: Testing an async function that uses await WITH: Angular 9, Jasmine 3.4.0 Minimal code to reproduce: StackBlitz I have a function like this. Note, that it has to await this.getHeaders(). Whenever I remove await and replace the implementation of getHeaders() by some synchonous implementation, the test runs successfully. What is the correct way to test it? private async loadUserData() { // Try to remove await - the test runs successfully //const headers = this.getHeaders(); const headers =

Xamarin.Forms Page.DisplayAlert in Page.OnAppearing

阅读更多关于 Xamarin.Forms Page.DisplayAlert in Page.OnAppearing

问题 I am unable to get a DisplayAlert popup to show within the OnAppearing callback of a Xamarin.Forms Page . Here is what I have tried so far: protected override void OnAppearing() { base.OnAppearing(); this.DisplayAlert("Alert", "Consider yourself alerted", "OK"); } Considering DisplayAlert is technically an async function, returning a Task , I have also tried the following: protected async override void OnAppearing() { base.OnAppearing(); await this.DisplayAlert("Alert", "Consider yourself

Will an instance be garbage collected if a Task's callback get reference to the instance itself?

阅读更多关于 Will an instance be garbage collected if a Task's callback get reference to the instance itself?

问题 public class Cls { public object Obj { get; set; } public async void Func() { Task.Run(() => { Thread.Sleep(999999999); this.Obj = new { }; }); } } public class Program { public static void Main(string[] args) { new Cls().Func(); } } Please consider the above codes and neglect if it makes sense first. In the above case, I did not store instance of Cls into any variable, seems that nothing is referencing that instance and it would be GC. However, there is a Task.Run() in side Func . The

file.slice fails second time

阅读更多关于 file.slice fails second time

问题 I'm trying to make a (front-end) Javascript that would be able to copy very large files (i.e. read them from a file input element and 'download' them using StreamSaver.js). This is the actual code: <html> <header> <title>File copying</title> </header> <body> <script src="https://cdn.jsdelivr.net/npm/web-streams-polyfill@2.0.2/dist/ponyfill.min.js"></script> <script src="https://cdn.jsdelivr.net/npm/streamsaver@2.0.3/StreamSaver.min.js"></script> <script type="text/javascript"> const

file.slice fails second time

阅读更多关于 file.slice fails second time

Getting Query object instead of results with Async/await function and npm-mysql

阅读更多关于 Getting Query object instead of results with Async/await function and npm-mysql

问题 I have this function which is async and i'm trying to make a simple query from npm-mysql db. let sortCategory = async (id) => { try { var sql = 'SELECT * FROM categories WHERE parent_id=?'; var results = await connection.query(sql, id); // console.log(results); return(results); } catch(err) { console.log(err); return false; } } But instead of results inside the results variable i just get the query object. Query { _events: [Object: null prototype] { error: [Function], packet: [Function],

Unexpected `await` inside a loop. (no-await-in-loop)

阅读更多关于 Unexpected `await` inside a loop. (no-await-in-loop)

问题 How Should I await for bot.sendMessage() inside of loop? Maybe I Need await Promise.all But I Don't Know How Should I add to bot.sendMessage() Code: const promise = query.exec(); promise.then(async (doc) => { let count = 0; for (const val of Object.values(doc)) { ++count; await bot.sendMessage(msg.chat.id, `💬 ${count} and ${val.text}`, opts); } }).catch((err) => { if (err) { console.log(err); } }); Error: [eslint] Unexpected `await` inside a loop. (no-await-in-loop) 回答1: If you need to send