Question

我无法弄清楚我如何将Promise范例应用于我的代码。我的代码并没有弄清楚它应该如何。最后2个查询未执行... 第一个（mainQuery）仅限于＆lt; = 5个项目，所以它应该足够快。管道应该是： query1.find（） - ＆gt;对于找到的所有元素 - > gt;如果元素是类型1 - > query2.count（） - ＆gt; if count == 0-＆gt;保存新对象

你能帮我解决一下吗？先感谢您，米歇尔

mainQuery.find().then(
        function(items){
            for (var i = 0; i < items.length; i++) {               
                if(items[i].get("type") == 1){         
                    var query = new Parse.Query("Invites");
                    //query.equalTo("userId","aaaaaaaa")
                    query.count().then(function(count){
                          console.log("why i don't see it in logs...??");
                          if (count == 0){
                            var invite = new Parse.Object("Invites");
                            //invite.set("userId", "aaaaaaa");
                            invite.save();
                          }
                        }, function(error){
                        response.error("Msgs lookup failed");
                    }); 
                }
            }
            response.success(items);
        },
        function(error) {response.error("Msgs lookup failed");
    });

Answer 1

我认为问题在于您在执行其他查询之前调用了response.success。代码看起来应该更像：

mainQuery.find().then(
    function(items){
        var promises = [];
        for (var i = 0; i < items.length; i++) {
            if(items[i].get("type") == 1){
                var query = new Parse.Query("Invites");
                //query.equalTo("userId","aaaaaaaa")
                // first promise which needs to be resolved
                var countPromise = query.count().then(function(count){
                    console.log("why i don't see it in logs...??");
                    if (count == 0){
                        var invite = new Parse.Object("Invites");
                        //invite.set("userId", "aaaaaaa");
                        // instead of an resolved object, we return another promise which will be resolved 
                        // before entering the success part below
                        return invite.save();
                    } else {
                        // if there is nothing to do, we return an promise which will be resolved with a dummy value
                        return Promise.as('nothing to do');
                    }
                });
                promises.push(countPromise);
            }
        }
        return Parse.Promise.when(promises).then(function (results) {
            // we only get in here when all promises aboth has been resolved
            response.success(items);
        });
    },
    function(error) {
        // if any of the requests fail, this method will be called
        response.error("Msgs lookup failed");
    });

您可以在官方文档中找到有关如何链接承诺的其他信息：https://parse.com/docs/js/guide#promises-promises-in-parallel

解析承诺和循环查询

1 个答案: