嵌套的猫鼬充满了希望 [英] Nested mongoose populate with promises

问题描述

我正在尝试填充如下所示的模型:

var Org = new mongoose.Schema({
        _id: {type: String, unique:true}, //this will be the org code
        name: String,
        level: String,
        children: [{type: String, ref: 'Org'}]
    });

//Orgs have children orgs, which themselves can have children orgs at N levels

考虑到一个组织，我想填充它的孩子们，以及它的孩子们的孩子，等等.我可以在N = 2个级别上完成此操作，例如:

     req.Model.findOne({_id: id}).populate('children').exec(function(err, doc){
        if (err){
            return next(err);
        }
        req.Model.populate(doc, {path: 'children.children'}, function(err, doc){
            if(err){
                return next(err);
            }
            return res.json(doc);
        });
    });

几个小时以来，即使在N = 2的情况下，我也一直在尝试使用Promise来完成上述任务.我认为，对于N = *级别，使用猫鼬具有内置实现的承诺会更清洁.

For hours now I have been trying to accomplish the above using promises, even at N=2. I think that for N = * levels, It would be cleaner to do so with promises which mongoose has a built in implementation of.

        req.Model.findOne({_id: id}).populate('children').exec()
        .then(function (doc){
            if(!treeView) {
                return doc;
            }
            return req.Model.populate(doc, {path: 'children.children'});
        })
        .then(function (doc){
            return res.json(doc);
        },function(err){
            return next(err);
        });

// treeView is a query string that lets me know that I need to populate the refs

我认为它应该按以下方式工作:

1. exec()返回一个promise，我在对then()的第一次调用中就开始处理它
2. 如果treeView为false，我返回doc，这被视为原始诺言的解决方案，因此调用了第二个then()处理函数.这确实发生了.
3. 如果treeView为true，则对Model.populate的调用将返回另一个Promise，第二次对then()的调用也将处理该Promise.

我遇到此错误:

{
   "status": "error",
   "serverTimestamp": "2014-07-24T18:23:02.974Z",
   "message": "\"function\" == \"undefined\""
}

我知道它到达第二个then()错误处理程序，因为我已经登录到控制台进行验证，但是我无法弄清楚为什么会这样.一旦使它起作用，我将尝试使其适用于N = *级，我想这将涉及递归地创建更多的Promise.我在这里看到了许多相关的问题，但并不是我真正需要的.

I know it gets to the second then()'s error handler, because I have logged out to the console to verify, but I cannot figure out why this is happening. Once I can get this to work, I will try to make it work for N=* levels, which I imagine would involve creating more promises recursively. I have seen many questions here related, but not exactly what I needed.

任何帮助将不胜感激.

Any help is greatly appreciated.

推荐答案

我能够使用mongoose模型返回的Mongoose许诺使嵌套的子文档在MongooseJS v4.1中填充工作.无需使用其他Promise库.

I was able to make nested subdocument populate work in MongooseJS v4.1 using the Mongoose promise returned from the mongoose model. No need to use another promise library.

var fuelOrderId = req.params.fuelOrderId;
fuelOrderModel.findById(fuelOrderId).populate('aircraftId')
.then(function(order){
    return fuelOrderModel.populate(order,
         {path: 'aircraftId.aircraftContacts', 
          model: 'aircraftContactModel'});
})
.then(function(result){
    res.json({
        fuelOrder: result,
        status: 1
    });
},function(err){
    console.error(err);
    res.json({err: err, status: 0});
})

编辑请考虑使用.catch()而不是第二个功能来处理错误. mpromise现在支持.catch().

Edit consider using .catch() instead of a second function for errors. mpromise now supports .catch().

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