在node.js代码中实现回调的问题

Randeep 发表于 Dev

兰迪普

我有这个node.js函数process（），它应该在调用时返回一个值。我在为我的process（）创建回调时遇到问题。该值仅应在从ec2.runInstances（params，function（err，data）调用）获得响应后才从process（）返回。

-------------来自app.js（express.js）的代码段--------------------

var createEngine = require('./ec2_create.js');
app.get('/create', function (req, res) {
    res.render('create', {
        status: createEngine.process()
    });

});

------------------------来自ec2_create.js的代码段-------------------- ---

function process(callback) {

    var status = null;
    // Create the instance
    ec2.runInstances(params, function (err, data) {
        if (err) {
            //console.log("Could not create instance", err); 
            status = "Could not create instance: " + err;
        } else {
            var instanceId = data.Instances[0].InstanceId;
            //console.log("Created instance", instanceId);
            status = "Created instance: " + instanceId;
        }

    });
    callback(status);
};

module.exports.process = process;

希拉鲁丁·阿勒丁

尝试如下

function ec2process(callback){

var status = null;
// Create the instance
ec2.runInstances(params, function(err, data) {
if (err) { 
    //console.log("Could not create instance", err); 
    status = "Could not create instance: " + err;   
    }
else{
    var instanceId = data.Instances[0].InstanceId;
    //console.log("Created instance", instanceId);
    status = "Created instance: " + instanceId; 
  } 
callback(status); // Callback moved

});


};