asynccallback

问题 I have nodejs accessing a database to retrieve a row of orders. The following function is defined in a file called orderDb.js module.exports.getWaitingOrders = function getWaitingOrders(callback) { pool.query("SELECT * FROM live_order_table WHERE isWaiting = 1;", function(err, rows, fields) { if (err) { return new Error('Db error: ' + err); } if (rows.length <= 0) { return new Error("No results"); //Is this recommended? return [];// or this? } rows.forEach(function(row) { var order = {

问题 This question already has answers here : Is it possible to await an event instead of another async method? (9 answers) Closed 2 months ago . I'm trying to await a callback that is fired when a button is pressed. The important point is that I want to wait for the callback from a simple await without reshaping the code. In other words I want to achieve the following: internal async Task BatchLogic() { ProgressMessage = "Batch Logic Starts"; await OnCallbackFired(); ProgressMessage = "Batch

问题 I am trying to wrap my head around callbacks and I do not understand how callbacks guarantee that a statement will execute after(in terms of time) another statement which takes an unknown amount of time. I do not care about promises,await,async, etc but just plain callbacks as I am trying to learn. For example below, my method will execute the callback before the unknown time event has occured. I can see how callbacks can be used to execute something because an event occurred but not how they

问题 I'm trying to create a proxy with node-http-proxy in Node.js that checks whether a request is authorized in a mongodb. Basically, I created a middleware module for the node-http-proxy that I use like this: httpProxy.createServer( require('./example-middleware')(), 9005, 'localhost' ).listen(8005) What the middleware module does is using mongojs to connect to mongodb and run a query to see if the user is authorized to access the resource: module.exports = function(){ // Do something when first

问题 Essentially, what are the differences between these beyond the obvious? When should I use which form? class What { public Go() { Thread thread = new Thread(new ThreadStart(Go2)); thread.Background = true; thread.Start(); } private Go2() { using UdpClient client = new UdpClient(blabla) { while (stuff) { client.Receive(guh); DoStuff(guh); } } } } versus class Whut { UdpClient client; public Go() { client = new UdpClient(blabla); client.BeginReceive(guh, new AsyncCallback(Go2), null); } private

问题 I'm learning socket programming and I have the following function: public void OnDataReceived(IAsyncResult asyn) and this is how the callback gets set: pfnWorkerCallBack = new AsyncCallback(OnDataReceived); The problem is I need to pass another argument to OnDataReceived callback function, how can I do this? I'm trying to make a simple tcp server and I need to track from which client the data is coming from. Any tips? Thanks! 回答1: I'm going to presume you're using System.Net.Sockets.Socket

问题 I'm injecting a component into my web2py page using {{=LOAD(...)}} as described at http://web2py.com/books/default/chapter/29/12/components-and-plugins#LOAD, but I need to fire off some javascript once the component is loaded. Normally if something is loaded via ajax, there is a success callback. How can I set one of this via {{=LOAD(...)}} in web2py? 回答1: The simplest approach would be to set response.js in the controller of the component: def mycomponent(): response.js = 'alert("mycomponent

问题 function jsoncall(){ $.getJSON("http://localhost:3000/data", function (data) {...}); $.getJSON("http://localhost:3000/data", function (data) {...}); } jsoncall.callback(function(){ //do stuff }); Something like the pseudocode above. Is there a method in JavaScript that considers async calls like the getJSON above? 回答1: Use Deferred : [https://api.jquery.com/jquery.deferred/][1] function jsoncall(){ var $def = $.Deferred(); $.getJSON("http://localhost:3000/data", function (data) { $def.resolve

问题 I create a small script to understand callback better. From the below script, the behavior I expected was: "http.get runs and takes on average 200 ms. The for loop "i" increment takes on average 2500 ms. At 200 ms, the process should exit and the script should have stopped to work. Why is it printing all of i? If I understand this better, I think I understand callback. var http = require("http"); var starttime = new Date(); //Function with Callback for (var j =0; j<10; j++){ http.get({host :

问题 I developed a GWT application and make a AsyncCallback a jfreechart generated in server side. But there is an error returning a InvocationException. The detailed error message is here 404 html com.google.gwt.user.client.rpc.impl.RequestCallbackAdapter.onResponseReceived(RequestCallbackAdapter.java:209) callback.onResponseReceived(this, response); I used GWT 2.5.1 and jre7 and eclipse juno 4.2 My Service Interface, Asynchronous Interface and Implementing Service codes are the same as this