带有异步库的循环内的 Mongoose 异步调用

Question

我刚开始使用 nodejs/mongoose，我想我有一个典型的异步问题。有人可以指导我如何解决这个异步问题吗？

我有这个函数 "getAreasRoot" 并且在里面我有一个循环来用另一个异步函数的结果填充子项。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

您有 2 个任务：获取根，然后使用根获取 children。

如果我要使用 async.js 来执行此操作，我会使用 async.waterfall and async.mapSeries 的组合。我们使用 .waterfall 是因为我们想将第一个任务的结果传递给第二个任务。我们使用 .mapSeries 是因为我们想改变每个根区域的名称和 children.

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);
};

使用它

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

一边

Mongoose 操作是异步的，所以

doc.children = self.model("Area").getAreasChildren(...)

不正确，因为您返回的 Promise 与实际文档相反。

还有

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

带有异步库的循环内的 Mongoose 异步调用

Mongoose async call inside a loop with async library

mongoose

mongodb

node.js

async.js

mongoose-schema