Mongoose填充嵌入式 [英] Mongoose populate embedded
问题描述
我使用Mongoose.js并且无法解决3级层次结构文档的问题。
I use Mongoose.js and cannot solve problem with 3 level hierarchy document.
有2种方法可以做到。
首先 - 没有参考。
C = new Schema({
'title': String,
});
B = new Schema({
'title': String,
'c': [C]
});
A = new Schema({
'title': String,
'b': [B]
});
我需要显示C记录。我怎么能填充/找到它,只知道C的_id?
I need to show C record. How can i populate / find it, knowing only _id of C?
我尝试使用:
A.findOne({'b.c._id': req.params.c_id}, function(err, a){
console.log(a);
});
但我不知道如何从者返回一个只需要对象的对象。
But i dont know how to get from returnet a object only c object that i need.
第二如果使用refs:
C = new Schema({
'title': String,
});
B = new Schema({
'title': String,
'c': [{ type: Schema.Types.ObjectId, ref: 'C' }]
});
A = new Schema({
'title': String,
'b': [{ type: Schema.Types.ObjectId, ref: 'B' }]
});
如何填充所有B,C记录以获得层次结构?
How to populate all B, C records to get hierarchy?
我尝试使用这样的东西:
I was try to use something like this:
A
.find({})
.populate('b')
.populate('b.c')
.exec(function(err, a){
a.forEach(function(single_a){
console.log('- ' + single_a.title);
single_a.b.forEach(function(single_b){
console.log('-- ' + single_b.title);
single_b.c.forEach(function(single_c){
console.log('--- ' + single_c.title);
});
});
});
});
但是它将为single_c.title返回undefined。我有办法填充吗?
But it will return undefined for single_c.title. I there way to populate it?
谢谢。
推荐答案
In Mongoose 4您可以在多个级别填充文档:
In Mongoose 4 you can populate documents across multiple levels:
假设您有一个用户架构,可以跟踪用户的朋友。
Say you have a User schema which keeps track of the user's friends.
var userSchema = new Schema({
name: String,
friends: [{ type: ObjectId, ref: 'User' }]
});
首先 populate()
让你得到一个用户朋友列表。但是,如果您还想要用户的朋友朋友呢?在这种情况下,您可以指定填充
选项,告诉mongoose填充所有用户朋友的 friends
数组:
Firstly populate()
lets you get a list of user friends. But what if you also wanted a user's friends of friends? In that case, you can specify a populate
option to tell mongoose to populate the friends
array of all the user's friends:
User.
findOne({ name: 'Val' }).
populate({
path: 'friends',
// Get friends of friends - populate the 'friends' array for every friend
populate: { path: 'friends' }
});
取自: http://mongoosejs.com/docs/populate.html#deep-populate
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