Question

我遇到问题listsQuery在所有内容都被发送到浏览器时没有执行。我知道我需要一个承诺或其他东西，但我的尝试到目前为止都没有成功。救命啊！

function processNavigation(navigation) {
var nav = [];
_.each(navigation, function(navItems) {
    var navProperties = {
        name: navItems.get("Name"),
        longName: navItems.get("LongName"),
        icon: navItems.get("Icon"),
        url: navItems.get("Url"),
        module: navItems.get("Module"),
        runScript: navItems.get("RunScript"),
        sortOrder: navItems.get("SortOrder")
    };

    switch (navItems.get("Module")) {
        case "lists":
            var listsQuery = new Parse.Query("ListItems"); // This should return back! But it's async? Needs promise?
            listsQuery.ascending("SortOrder");
            listsQuery.find().then(
                function(results) {
                    var list = [];
                    _.each(results, function(listItems) {
                        var listProperties = {
                            name: listItems.get("Name"),
                            subName: listItems.get("Subname"),
                            sortOrder: listItems.get("SortOrder")
                        };
                    });
                    list.push(listProperties);
                    navProperties["source"] = list;
                },
                function() {
                    res.send('error');
                }
            );  
            break;

        default:
            navProperties["source"] = null;
            break;
    }

    nav.push(navProperties);
});

res.send(nav);
}

Answer 1

这应该会给你一些事情，我不确定它是否会奏效，但它应该向你展示这个概念。

您需要做的是创建一个promises数组，因为它看起来像是对数组中的每个项执行查询，并且因为查询需要一些时间才能在查询完成之前发送响应。然后，您可以评估承诺数组，并仅在解决后发回您的回复。

我建议你将逻辑分成几个函数，因为它有点难以理解。

查看parallel promises section

function processNavigation(navigation) {
    var nav = [];
    var promises = []

        _.each(navigation, function(navItems) {
            var navProperties = {
                name: navItems.get("Name"),
                longName: navItems.get("LongName"),
                icon: navItems.get("Icon"),
                url: navItems.get("Url"),
                module: navItems.get("Module"),
                runScript: navItems.get("RunScript"),
                sortOrder: navItems.get("SortOrder")
            };

            switch (navItems.get("Module")) {
                case "lists":
                    promises.push((function(navProperties){
                        var listsQuery = new Parse.Query("ListItems"); // This should return back! But it's async? Needs promise?
                        listsQuery.ascending("SortOrder");
                        listsQuery.find().then(
                            function(results) {
                                var list = [];
                                _.each(results, function(listItems) {
                                    var listProperties = {
                                        name: listItems.get("Name"),
                                        subName: listItems.get("Subname"),
                                        sortOrder: listItems.get("SortOrder")
                                    };
                                });
                                list.push(listProperties);
                                navProperties["source"] = list;
                                promise.resolve();
                            },
                            function() {
                                promise.reject();
                                res.send('error');
                            }
                        );
                    })(navProperties))

                    break;

                default:
                    navProperties["source"] = null;
                    break;
            }

            nav.push(navProperties);
        });


        Parse.Promise.when(promises).then(function(){                               
            res.send(nav);
        })

    }

事后Parse.com查询执行

1 个答案: