Javascript 从Node.js应用程序中的模型层异步返回数据

我正在开发一个节点应用程序，并用一个单独的模型层来组织代码。该模型有一个名为getImages的函数，它利用Mongojs模块从数据库中获取信息。问题是getImages在检索数据之前返回。我习惯于使用同步代码，所以这个问题很难让我理解。我怀疑答案是采用回调函数。有人能告诉我这是怎么回事吗？或者，如果回调不是解决方案，那么是什么

routes/index.js

exports.image = function(req, res) {
if (req.method == 'GET') {

    var image = model.getImages();
    return res.send(image);        
}
}

var getImages = function() {

    var imagesCollection = db.collection('Images');

    var images = imagesCollection.find(function(err, docs) {
        return docs;
    });

    return images;
}

exports.getImages = getImages;

exports.image = function(req, res) {
    if (req.method == 'GET') {
        model.getImages(function(err, images) {
            return res.send(images);        
        });
    }
}

var getImages = function(callback) {

    var imagesCollection = db.collection('Images');

    imagesCollection.find(callback);
}

exports.getImages = getImages;

models/index.js

exports.image = function(req, res) {
if (req.method == 'GET') {

    var image = model.getImages();
    return res.send(image);        
}
}

var getImages = function() {

    var imagesCollection = db.collection('Images');

    var images = imagesCollection.find(function(err, docs) {
        return docs;
    });

    return images;
}

exports.getImages = getImages;

exports.image = function(req, res) {
    if (req.method == 'GET') {
        model.getImages(function(err, images) {
            return res.send(images);        
        });
    }
}

var getImages = function(callback) {

    var imagesCollection = db.collection('Images');

    imagesCollection.find(callback);
}

exports.getImages = getImages;

---

您需要为

getImages

函数提供回调参数。例如：

routes/index.js

exports.image = function(req, res) {
if (req.method == 'GET') {

    var image = model.getImages();
    return res.send(image);        
}
}

var getImages = function() {

    var imagesCollection = db.collection('Images');

    var images = imagesCollection.find(function(err, docs) {
        return docs;
    });

    return images;
}

exports.getImages = getImages;

exports.image = function(req, res) {
    if (req.method == 'GET') {
        model.getImages(function(err, images) {
            return res.send(images);        
        });
    }
}

var getImages = function(callback) {

    var imagesCollection = db.collection('Images');

    imagesCollection.find(callback);
}

exports.getImages = getImages;

models/index.js

exports.image = function(req, res) {
if (req.method == 'GET') {

    var image = model.getImages();
    return res.send(image);        
}
}

var getImages = function() {

    var imagesCollection = db.collection('Images');

    var images = imagesCollection.find(function(err, docs) {
        return docs;
    });

    return images;
}

exports.getImages = getImages;

exports.image = function(req, res) {
    if (req.method == 'GET') {
        model.getImages(function(err, images) {
            return res.send(images);        
        });
    }
}

var getImages = function(callback) {

    var imagesCollection = db.collection('Images');

    imagesCollection.find(callback);
}

exports.getImages = getImages;

---

似乎您是imagesCollection.find是异步函数。以下是您可以尝试的代码

var getImages = function(callback) {

  var imagesCollection = db.collection('Images');

  imagesCollection.find(function(err, docs) {
     if (err) {
       callback(null);
     } else {
        callback(docs);
     }

  });

}


exports.getImages = getImages;
exports.image = function(req, res) {

 var imageDataFunc = function(imageDataFromDB) {
  if(imageDataFromDB) {
     res.send(imageDataFromDB);
     res.end();
  }

 }

 if (req.method == 'GET') {
   model.getImages(imageDataFunc);        
 }
}

---

谢谢在我看来，这很简单。