Node.js Q承诺多个参数

Question

试图在我的nodejs express应用程序中使用Q promise库来清理我的回调面条代码，但我在翻译它的某些部分时遇到了麻烦。在向函数传递多个参数和处理作用域时遇到麻烦。

这里是一个简化的"同步"版本来展示我的逻辑:

function updateFacebook(req, res) {
    var user = getUserFromDB(userid);
    var profile = getUserProfileFromAPI(accessToken);
    var success = updateUserDB(user, profile);
    res.json({ result: success });
}

我将回调函数转换为返回承诺

function getUserFromDB(userid) {
    var deferred = Q.defer();
    // somewhere in here there's a deferred.resolve(user object);
    queryMongo()...
    return deferred.promise;
}
function getUserProfileFromAPI(accessToken) {
    var deferred = Q.defer();
    // somewhere in here there's a deferred.resolve(profile object);
    request()...
    return deferred.promise;
}
function updateUserDB(user, profile) {
    var deferred = Q.defer();
    // somewhere in here there's a deferred.resolve(updated user object);
    updateMongo()...
    return deferred.promise;
}
function handleResponse(res, user) {
    var deferred = Q.defer();
    // was thinking about putting the res.json here
    // i have no way of passing in the res
    // and res is out of scope...
    res.json({});
    return deferred.promise;
}

现在的问题是连接它们，我试过…

Q.when(getUserFromDB(userid), getUserProfileFromAPI(accessToken))
 .spread(updateUserDB)
 .done(handleResponse);
Q.all([getUserFromDB(userid), getUserProfileFromAPI(accessToken)])
 .spread(updateUserDB)
 .done(handleResponse);

超级困惑。任何指导都将不胜感激。

Answer 1

看起来您的handleResponse期望两个参数，但updateUserDB只解析一个对象。你可以这样做:

function getResponseHandler(res) {
    return function(user) {
        // your handleResponse code here
        // which now has access to res
    }
}

，然后命名为:

Q.all([getUserFromDB(userid), getUserProfileFromAPI(accessToken)])
 .spread(updateUserDB)
 .done(getResponseHandler(res));