Question

我刚开始使用nodejs / mongoose，我认为我有一个经典的异步问题。有人可以指导我如何解决这个异步问题吗？

我有这个功能＆＃34; getAreasRoot＆＃34;在里面我有一个循环来填充孩子与另一个异步函数的结果。如何使用异步库修复它？

areaSchema.statics.getAreasRoot = function(cb: any) {
    let self = this;
    return self.model("Area").find({ parentId: null }, function(err: any, docs: any){
        docs.forEach(function(doc: any){
            doc.name = "Hi " + doc.name;
            doc.children = self.model("Area").getAreasChildren(doc._id, function(err: any, docs: any){});
        })
        cb(err, docs);
    });
};

areaSchema.statics.getAreasChildren = function(id: any, cb: any) {
    return this.model("Area").find({ parentId: null }).exec(cb);
}

Answer 1

你有两个任务：获得根，然后让孩子使用根。

如果我使用async.js执行此操作，我会使用async.waterfall和async.mapSeries的组合。我们使用if (this.originalFrom > addFrom) { this.dataService.addTimeSlots(details).then((result) => { console.log(result); }, (err) => { console.log(err); }); } if (this.originalTo < addTo) { this.dataService.addTimeSlots(details2).then((result) => { console.log(result); }, (err) => { console.log(err); }); } if (this.originalTo > addTo) { this.dataService.addTimeSlots(details3).then((result) => { console.log(result); }, (err) => { console.log(err); }); } some_Page_Closing_Function_When_All_Callbacks_Are_Done();因为我们想要将第一个任务的结果传递给第二个任务。我们使用.waterfall因为我们想要改变每个根区域的名称和子项。

.mapSeries

使用它

areaSchema.statics.getAreasRoot = function (cb) {
    let self = this;
    async.waterfall([
        // every task has a callback that must be fired at least/most once
        // to tell that the task has finished OR when an error has occurred
        function getRoots (cb1) {
            self.find({ parentId: null }, cb1);
        },
        function getChildren (roots, cb2) {
            async.mapSeries(roots, function (root, cb3) {
                // inside this block, we want to fire the innest callback cb3 when 
                // each iteration is done OR when an error occurs to stop .mapSeries
                self.find({ parentId: root._id }, function (err, children) {
                    // error: stop .mapSeries
                    if (err)
                        return cb3(err);
                    root.name = "Hi " + root.name;
                    root.children = children;
                    // done: send back the altered document
                    cb3(null, root);
                });
            // the last argument is fired when .mapSeries has finished its iterations
            // OR when an error has occurred; we simply pass the inner callback cb2
            }, cb2) 
        }
    // the last argument is fired when .waterfall has finished its tasks
    // OR when an error has occurred; we simply pass the original callback cb
    ], cb);
};

<强>除了

Mongoose操作是异步的，所以

Area.getAreasRoot(function (err, areas) {
    console.log(err, areas);
})

不正确，因为您正在返回与实际文档相对的Promise。

同时

您可能能够使用virtual population或aggregation简化您的逻辑。

使用异步库在循环内进行Mongoose异步调用

1 个答案: