嵌入式文档的猫鼬更新

Posted 2023-03-10

【中文标题】嵌入式文档的猫鼬更新

【英文标题】：Mongoose update of embedded document

【发布时间】：2012-04-29 21:41:13

【问题描述】：

我正在慢慢发疯，试图了解如何在 mongoose 中更新嵌入文档的值，并编写了一些演示该问题的 node.js 代码。

var mongoose = require('mongoose');
var Schema = mongoose.Schema;

mongoose.connect('mongodb://localhost/mongoose_broken');

var ASchema = new Schema(
   value :  type: String, index:  unique: true  ,
   bs    : [BSchema],
);
var BSchema = new Schema(
   value :  type: String ,
);
var A = mongoose.model('A', ASchema);
var B = mongoose.model('B', BSchema);

// Add an entry of A, with 1 embedded B
//
var a = new A();
a.value = "hello";
var b = new B();
b.value = "world";
a.bs.push(b);

a.save(function(err) 
   if (err) 
      console.log("Error occured during first save() " + err);
      return;
   

   // Now update a by changing a value inside the embedded b
   //
   A.findOne( value: 'hello' , function(err, doc) 
      if (err)  console.log("Error occured during find() " + err); return; 

      doc.bs[0].value = "moon";

      doc.save(function(err) 
         if (err) console.log("Error occuring during second save()");

         // Check b was updated?
         //
         if (doc.bs[0].value != "moon") 
            console.log ("b was not updated! (first check)");   
          else 
            console.log ("b looks like it was updated (first check)");

            // Do a fresh find
            //
            A.findOne(value: "hello", function(err, doc_2) 
               if (err)  console.log("Error occured during second find() " + err); return; 

               if (doc_2.bs[0].value != "moon") 
                  console.log ("b was not updated! (second check)");   
                else 
                  console.log ("b looks like it was updated (second check)");
               
            );
         
      );
   );
);

运行的输出是：

b looks like it was updated (first check)
b was not updated! (second check)

知道为什么嵌入文档的更新没有保存吗？

【问题讨论】：

如果你这样做了console.log(doc_2.bs);，它对 doc_2 有什么看法

console.log(doc_2.bs) 打印“[[Object object]]”并且 console.log(doc_2.bs[0]) 给出“ value: 'world', _id: 4f8ee35f8228240f43000002 "

【参考方案1】：

您必须先声明子架构，然后才能在父架构中使用它们。

var BSchema = new Schema(
  value :  type: String ,
);    
var ASchema = new Schema(
  value :  type: String, index:  unique: true  ,
  bs    : [BSchema],
);

【讨论】：

你明白了 - 修复了它。我建议它是一个错误，因为如果你引用一个不存在的模式你会得到一个错误，但当它们出现故障时不会......非常出乎意料！无论如何，知道这已经解决了，我今晚可以睡得安稳了 - 谢谢 Aaron :)

它是一个叫做“提升”的js东西adequatelygood.com/2010/2/javascript-Scoping-and-Hoisting