同步Meteor.methods函数内的MeteorJS异步代码 [英] MeteorJS async code inside synchronous Meteor.methods function

问题描述

如何让客户端method.call等待异步函数完成？目前它到达函数的末尾并返回undefined。

How to get the client method.call to wait for an asynchronous function to finish? Currently it reaches the end of the function and returns undefined.

Client.js

Client.js

Meteor.call( 'openSession', sid, function( err, res ) {
    // Return undefined undefined
    console.log( err, res ); 
});

Server.js

Server.js

Meteor.methods({
    openSession: function( session_id ) {
        util.post('OpenSession', {session: session_id, reset: false }, function( err, res ){
            // return value here with callback?
            session_key = res;
        });
     }
});

推荐答案

Meteor的最新版本提供了无证件 Meteor._wrapAsync 函数将函数转换为标准（错误，res）回调到同步函数，意味着当前光纤在回调返回之前产生，然后使用Meteor.bindEnvironment确保保留当前的Meteor环境变量（例如 Meteor.userId（））。

Recent versions of Meteor have provided the undocumented Meteor._wrapAsync function which turns a function with a standard (err, res) callback into a synchronous function, meaning that the current Fiber yields until the callback returns, and then uses Meteor.bindEnvironment to ensure that you retain the current Meteor environment variables (such as Meteor.userId()).

一个简单的用法如下：

asyncFunc = function(arg1, arg2, callback) {
  // callback has the form function (err, res) {}

};

Meteor.methods({
  "callFunc": function() {
     syncFunc = Meteor._wrapAsync(asyncFunc);

     res = syncFunc("foo", "bar"); // Errors will be thrown     
  }
});

您可能还需要使用 function＃bind 确保在包装之前使用正确的上下文调用 asyncFunc 。
有关详细信息，请参阅： https://www.eventedmind.com/tracks/feed -archive / meteor-meteor-wrapasync

You may also need to use function#bind to make sure that asyncFunc is called with the right context before wrapping it. For more information see: https://www.eventedmind.com/tracks/feed-archive/meteor-meteor-wrapasync

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