mongodb 了解 Mongoose 中的关系和外键
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Understanding Relationships & Foreign Keys in Mongoose
提问by Jiew Meng
In MongoDB/Mongoose, how do I define a relationship? I think there are a few ways I've seen, but I'm not sure I understand the differences or when do I use which. I am using Mongoose 3
在 MongoDB/Mongoose 中，如何定义关系？我想有几种方法我见过，但我不确定我是否理解这些差异，或者我什么时候使用哪个。我正在使用猫鼬 3
I've defined Todoand TodoListmodel, where the relationship is obvious. So following the docs http://mongoosejs.com/docs/documents.html, I've defined classes like:
我已经定义Todo和TodoList建模，其中的关系很明显。因此，按照文档http://mongoosejs.com/docs/documents.html，我定义了如下类：
# Todo.coffee
mongoose = require "mongoose"
todoSchema = mongoose.Schema
name: String
desc: String
dueOn: Date
completedOn: Date
module.exports = mongoose.model "Todo", todoSchema
# TodoList.coffee
mongoose = require "mongoose"
Todo = require "./Todo"
todoListSchema = mongoose.Schema
name: String
todos: [Todo.schema]
module.exports = mongoose.model "TodoList", todoListSchema
Then I tried testing the classes:
然后我尝试测试这些类：
list = new TodoList
name: "List 1"
todos: [
{ name: "Todo 1", desc: "Hello", dueOn: new Date(2012,10,1), completedOn: new Date(2012,10,2) }
{ name: "Todo 2" }
{ name: "Todo 3", desc: "Hello 2", dueOn: new Date(2012,10,6), completedOn: new Date(2012,10,2) }
{ name: "Todo 4" }
]
#list.todos.push { name: "Todo 5" }
console.log "List", list
list.save (err) ->
if !err
TodoList.find {}, (err, lists) ->
console.log "TODOS"
console.log lists.length, lists
done(err)
else
console.log "ERROR!!!"
done err
When I try to do Todo.find()I get nothing, so the Model (Todo.coffee) is kind of redundant? It looks like Todoare stored in TodoList, as a user I may not care, but I wonder what are the implications? Eg. will the document get too large? 1 TodoList with too many Todos? Does that matter? What if I allow nested Todos (not that I want to do itm just for understanding), is it better to store documents separately then? How do I do that, if I so desire, and when do I do it?
当我尝试做Todo.find()我一无所获时，所以模型 ( Todo.coffee) 有点多余？看起来Todo存储在 中TodoList，作为用户我可能不在乎，但我想知道有什么含义？例如。文档会不会太大？1 TodoList 有太多 Todos？这有关系吗？如果我允许嵌套的 Todos（不是我想这样做只是为了理解），那么单独存储文档会更好吗？如果我愿意，我该怎么做，什么时候做？
I saw another method, in Mongoose 2 actually, dunno if its possible in 3, something like using ObjectIdinstead of nested docs. Maybe thats to store it separately?
我看到了另一种方法，实际上在 Mongoose 2 中，不知道是否可以在 3 中使用，例如使用ObjectId而不是嵌套文档。也许那是分开存放？
回答by ZachRabbit
I'm still new to Node, Mongoose, and Mongo, but I think I can address at least part of your question. :)
我还是 Node、Mongoose 和 Mongo 的新手，但我想我至少可以解决您的部分问题。:)
Your current method is the same as I tried doing at first. Basically, it ends up storing it very similarly to this (written in JS, since I don't know CoffeeScript):
您当前的方法与我最初尝试的方法相同。基本上，它最终的存储方式与此非常相似（用 JS 编写，因为我不知道 CoffeeScript）：
var todoListSchema = new mongoose.Schema({
name: String,
todos: [{
name: String,
desc: String,
dueOn: Date,
completedOn: Date
}]
});
I later found this method, which is what I was looking for, and I think what you were intending:
后来我找到了这个方法，这就是我要找的，我想你的意图是：
var todoListSchema = new mongoose.Schema({
name: String,
todos: [{
type: mongoose.Schema.Types.ObjectId,
ref: 'Todo' //Edit: I'd put the schema. Silly me.
}]
});
This stores an array of ObjectIds, which you can then load using Query#populatein Mongoose.
这存储了一个 ObjectIds 数组，然后您可以Query#populate在 Mongoose 中使用它加载。
I don't know of the technical implications, but it makes more sense in my brain if I keep them separate, so that's what I'm doing. :)
我不知道技术上的含义，但如果我将它们分开，我的大脑会更有意义，所以这就是我正在做的。:)
Edit: Here is a some official docs that might be useful: http://mongoosejs.com/docs/populate.html
编辑：这是一些可能有用的官方文档：http: //mongoosejs.com/docs/populate.html
