解析：Query.find 在循环内找不到数据（即使在使用承诺之后）

Question

我实际上传递了两个列表（existingLeaderboard 和 newResultSetObj），我正在根据某种逻辑比较和查询它们。最后我想根据逻辑向每个用户发送通知。但不知何故，我的代码不等待查找查询（控制台日志永远不会出现在日志中）。这是代码 -

function compareAndSendNotification(existingLeaderboard, newResultSetObj) {
        var _ = require('underscore');
        var leadboardarray=[];
        console.log("New leaderboard" + newResultSetObj);
        console.log("Existing leaderboard" + existingLeaderboard);
        leadboardarray = existingLeaderboard;


        if (typeof existingLeaderboard == "undefined" || typeof newResultSetObj == "undefined"
            || existingLeaderboard.length == 0 || newResultSetObj.length == 0) {
            console.log("existingLeaderboard or newResultSetObj is null");
            return true;
        }

        var getUserFromLookPromise = Parse.Promise.as();

            var fromUser = "";
            //Event out looks


            _.each(existingLeaderboard, function(test) {
                if (contains(newResultSetObj, test)) {
                    console.log("Look id still in top 3 i =" + test);
                    // get user from look
                    var lookId = test;
                    console.log('get look id called ' + lookId);

                    var look = Parse.Object.extend("Look");
                    var lookQuery = new Parse.Query(look);
                    lookQuery.equalTo("objectId", lookId);

                    console.log("before find query");

                    //getUserFromLookPromise=getUserFromLookPromise.then(function(){
                    //     return lookQuery.find();
                    lookQuery.find().then(function(){
// following console log never prints 
                        console.log("inside find query");
                        var lookqueryPromise = Parse.Promise.as();
                        lookqueryPromise = lookqueryPromise.then(function() {
                            return lookQuery.find();
                        });
                        //while(lookqueryPromise.find().length==0){
                        //    lookqueryPromise.resolve(lookQuery.find());
                        //}
                        return lookqueryPromise;

                    }).then(function (notificationUser) {
                        console.log("inside resolve user");
                        if ( typeof notificationUser == "undefined" || notificationUser.length == 0 ) {
                            getUserFromLookPromise.resolve(notificationUser);
                        }
                        fromUser = notificationUser[0].get['fromUser'];
                        return fromUser;
                    }).then(function (user) {
                        console.log("sending notification to user " + user);
                        sendNotification(user, "hello");
                    });


                }
            });

        return getUserFromLookPromise;

    }

我是解析新手。请让我知道我做错了什么。

Answer 1

让我们从一个较小的问题开始：获取一个 "Look" 对象给定它的 id:

function lookWithId(objectId) {
    var query = new Parse.Query("Look");
    query.include("fromUser");  // presumes "fromUser" is a pointer to Parse.User
    return query.get(objectId);
}

现在，让我们使用该函数来解决一个更大的问题：在给定 id 数组的情况下获取 "Look" 个对象的数组：

var _ = require('underscore');

function looksWithIds(objectIds) {
    var promises = _.map(objectIds, function(objectId) {
        return lookWithId(objectId);
    });
    return Parse.Promise.when(promises);
}

现在更难了。给定一组用户，向每个用户发送一条消息。仅当您的应用通过在每个安装上设置 "user" 指针将安装与用户相关联时，才能完成此操作。

function sendMessageToUser(user) {
    var query = new Parse.Query(Parse.Installation);
    query.equalTo('user', user);
    return Parse.Push.send(where: query, data: { alert: "Hello" });
}

然后像我们之前那样将那个复数化...

function sendMessagesToUsers(users) {
    var promises = _.map(users, function(user) {
        return sendMessageToUser(user);
    });
    return Parse.Promise.when(promises);
}

您编写的另一个函数：给定两个排行榜，return 满足某些应用程序条件的 "Look" 个对象 ID 数组...

function lookIdsFromLeaderBoards(leaderBoardA, leaderBoardB) {
  // written by @user2922400, based on the app
  // no promises needed here, just answer an array of Look object ids
}

现在，您尝试的功能非常简单：

function sendMessagesToLeader(leaderBoardA, leaderBoardB) {
    var lookIds = lookIdsFromLeaderBoards(leaderBoardA, leaderBoardB);
    return looksWithIds(lookIds).then(function(lookObjects) {
        var users = _.map(lookObjects, function(lookObject) {
            return lookObject.get("fromUser");
        });
        return sendMessagesToUsers(users);
    })
}

解析：Query.find 在循环内找不到数据（即使在使用承诺之后）

Parse: Query.find does not find data inside loop (even after using promises)

javascript

promise

parse-platform

parse-cloud-code