Promise... 返回类型而不是 Promise<Type>

Question

I'm trying to achieve something that seems impossible in typescript due to it's asynchronous nature.

I basically have a net.Socket object to communicate with a server through TCP protocole.

Here is what I would like to achieve :

 import * as net from 'net' class TCPClient { // The member used to communicate with the server client: net.Socket; [...] /** * Method called in another portion of code. * In this method, I call client.write to send data to server. * As first param, I put the command. As second param, a callback that is called when the * data is sent. * I listen then to the 'data' event to read the response from the server. * I store the response into a variable. I return the variable. * PROBLEM: Due to the asyncronous type of NodeJS, the variable appears as empty. **/ command(cmd: string): string{ var res : string; this.client.write(cmd, () => { this.client.on('data', response => { res = response.toString(); }); }); return res; } [...] }

Answer 1

You have to make an asynchroneous method using Promises, something like:

command(cmd: string): Promise<string> {
  return new Promise((resolve) => {
    this.client.write(cmd, () => {
      this.client.on('data', response => {
        resolve(response.toString());
      });
    });
  })
}

But to make it simpler you may use async/await in your calling code.