node.js - Mongoose:子文档CastError:Cast to Array失败

我有两种模式：
架构一（父级）：

var slide = require('../model/slide');

var slidesetSchema = new Schema({
    name: String,
    dataID: Schema.Types.ObjectId,
    slides: [slide]
});

子模式：

var slideSchema = new Schema();
// use this method for a recursive definiton
// src https://groups.google.com/forum/#!topic/mongoose-orm/0yUVXNyprx8
slideSchema.add({
    no: Number,
    depth: Number,
    audio: [{
        name: String,
        dataID: Schema.Types.ObjectId
    }],
    //subslides: [slideSchema] <- this will be the next step if the other problem is solved
    // it will be used to create a tree like structure
});

我有以下情况：用户上传一个pdf文件，然后nodejs服务器为该文件创建一个新条目（slideset），对于每个页面，它应该创建一个幻灯片并将其存储到slideset中。最后，整个事情应该保存到数据库中：

var set = new slideset();
var slides = [];

for (var i = 1; i <= pagecount; i++) {
    var s = new slide({no: i, depth: 1, audio: []});
    slides.push(s);
    // set.slides.push(s); <-- throws "can't call push of undefined",
    // well here http://mongoosejs.com/docs/subdocs.html they just do the same thing.. why doesn't it work for me?!
}
set.slides = slides;
// some other stuff, like writestream to save the file into db, set set.name and dataID
writestream.on('close', function (file) {
     // save schema
     set.save(function (err) {
         console.err(err);
     }
});

函数“save”引发以下错误：

ValidationError: CastError: Cast to Array failed for value "{...},{...},..." at path "slides"

我在stackoverflow上尝试了不同的可能解决方案，但都没有成功。我希望你能帮助我：-）

最佳答案

你试过了吗：

var Audio = new Schema({
       name: String,
       dataID: Schema.Types.ObjectId
});

然后

slideSchema.add({
    no: Number,
    depth: Number,
    audio: [Audio]
});

？