如何将sdtout从服务器返回到字符串中的客户端？ [英] How to return a sdtout from a server to a client inside a string?

问题描述

我正在尝试返回我的方法的 stdout ，但在客户端我总是有 undefined 尽管服务器说它是带有内容的字符串。

I'm trying to return the stdout of my method but on the client I always have undefined despite the server says it's a string with content.

我这样做：

'getExistingFiles': function () {
      var list = "";
      return new Promise(Meteor.bindEnvironment(function(resolve) {
        child = exec_tool("ls -al",
          function (error, stdout, stderr) {
            if (error !== null) {
              console.error('exec error: ' + error);
              list = "error: " + error;
              resolve(list);
              return list;
            }else{
              list = stdout;
              console.log(typeof list);
              console.log("LIST:------------");
              console.log(list);
              resolve(list);
              return list;
            }
          });
      }));
}

在我的终端上我有日志：

On my terminal I have the logs:

但是当我尝试访问该值时客户端 undefined ：

But on the client when I try to access the value it's undefined:

Meteor.call("getExistingFiles",function(list){
       console.log(list);
       console.log(typeof list);
});

所以我的问题是，我怎么能发送这个列表给客户？

So my question is, how could I send this list to the client ?

我试过这样测试一下我的客户是不是错了，但是我认为服务器上没有它

I tried like this to test if it was my client who was wrong but no it's on the server I think

//server      
var et = Meteor.wrapAsync(exec_tool);
 try {
  child = et('ls -al');
  console.log("LIST:------------");
  console.log(child);
  console.log(typeof child);
  return child;
 } catch (err) {
  throw new Meteor.Error(err, err.stack);
}

即使这样它也会发送 undefined 为什么？！

even like this it send a undefined WHY ?!

var et = Meteor.wrapAsync(exec_tool);
      try {
       var proc = exec_tool("ls -al")
       proc.stdout.on('data', function (data) {
         //do something with data
         console.log(data);
         list = list + data;
       });
       proc.stdout.on('end', function() {
         console.log("end");
         console.log(list);
         return list;
       });
      } catch (err) {
       throw new Meteor.Error(err, err.stack);
      }

推荐答案

在服务器上（承诺来自评估服务器，然后在完成后发送给客户端：

On the server (promises from the server are evaluated and then sent to the client when they're done):

getExistingFiles: function () {
      return new Promise((resolve, reject) => {
        child = exec_tool("ls -al",
          function (error, stdout, stderr) {
            if (error) {
              reject(error);
            } else {
              resolve(stdout);
            }
          });
      }));
}

在客户端：

Meteor.call("getExistingFiles", function(err, list) {
    if(err) {
        // handle your error
        throw err;
    }
    console.log(list);
});

承诺没有返回。来自异步函数的回调通常具有函数（错误，结果）参数列表。所以，想要的结果应该在第二个参数中。试试这样。

Promises don't have return. Callbacks from async functions usually have the function (error, result) argument list. So, the wanted result should be in the second argument. Try it like this.

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