mongoose连表查询2

1.解读mongoose的populate

    1.Query#populate

var mongoose = require('mongoose')
  , Schema = mongoose.Schema
  
var personSchema = Schema({
  _id     : Number,    // 只支持ObjectId,Number,String,Buffer，就这几个引用类型，ref匹配的只有这个_id

  name : String, 

  age : Number, 

  stories : [{ type: Schema.Types.ObjectId, ref: 'Story' }] }); 

var storySchema = Schema({ 
   _creator : { type: Number, ref: 'Person' }, 
　　title : String, fans : [{ type: Number, ref: 'Person' }] 
});

var Story = mongoose.model('Story', storySchema); 
var Person = mongoose.model('Person', personSchema);

_id的类型是:ObjectId, Number, String, and Buffer are valid for use as refs.
那么_crestor 存储的类型必须与这个_id的数据类型一直,只能关联_id.

在文档关联使用ref一定要注意，关联的那个model只能匹配_id这个字段，你要是搞个自动生成的啥的一概无效