Node.js：对象值作为child_process.exec的stdout [英] Node.js: Object value as stdout of child_process.exec

问题描述

我是Node的新手，对它的一些非阻塞性元素s之以鼻。我正在尝试创建一个对象，并将其元素之一作为返回child_process.exec的stdout的函数，如下所示：

I'm new to Node and stumbling on some of the nonblocking elements of it. I'm trying to create a object and have one of the elements of it being a function that returns the stdout of a child_process.exec, like so:

var exec = require('child_process').exec;
var myObj = {};

myObj.list = function(){
  var result;
  exec("ls -al", function (error, stdout, stderr) {
     result = stdout;
  });
  return result;
}
console.log('Ta da : '+myObj.list);

我认为 myObj.list 正在返回结果设置为 stdout 之前，但我不知道如何使其等待或执行回调为了它。谢谢您的帮助！

I figure that myObj.list is returning result before it is set as stdout, but I can't figure out how to make it wait or do a callback for it. Thanks for your help!

推荐答案

您无法直接返回该值，因为该值将不再可用。因此，代替返回值，您需要使用回调，这意味着将调用代码内外一点。

You can't directly return the value as it's not going to be available for a bit. So instead of a return value you need to use a callback which means turning the calling code inside out a bit.

var exec = require('child_process').exec;
var myObj = {};

myObj.list = function(callback){
  var result;
  exec("ls -al", function (error, stdout, stderr) {
     callback(stdout);
  });
  // No return at all!
}
// Instead of taking a return we pass a callback
// which receives the value and carries on our computation.
myObj.list(function (stdout) {
   console.log('Ta da : '+ stdout);
});

在实际代码中，您可能希望回调函数将错误作为第一个参数，不必这么做，但这是在Node.JS中完成的正常方法。

In real code you'd probably want to have your callback take an error as its first argument, you don't have to but it's the normal way things are done in Node.JS.

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