WeChat applet uses cloud functions to update and add cloud database nested array elements

需求

1. 更新 Update

Now there was a cloud databaseJson嵌套数组对象,request to update it list 中的 checked 字段值.数据如下：

{
    
	"book_id": "7-4",
	"book_words": [{
    
			"list": [{
    
				"checked": false,
				"eg": "Mrs. Rachel Lynde lived on the main road in Avonlea.",
				"meaning": "主要道路,⼤路",
				"word": "main road"
			}, {
    
				"checked": false,
				"eg": "At half -past three, Matthew Cuthbert was driving his buggy down the road.",
				"meaning": "30分",
				"word": "half"
			}],
			"title": "Anne of Green Gables 1_Mrs. Lynde Is Surprised",
			"unit_id": 1
		},
		{
    
			"list": [{
    
				"checked": false,
				"eg": "She saw the odd girl in the ugly dress.",
				"meaning": "奇怪的,奇特的",
				"word": "odd"
			}, {
    
				"checked": false,
				"eg": "She saw the odd girl in the ugly dress, with long red braid s and big eyes.",
				"meaning": "发辫,辫⼦",
				"word": "braid"
			}],
			"title": "Anne of Green Gables 1_Mrs. Lynde Is Surprised",
			"unit_id": 2
		}

	]
}

.
更新有 set 和 update 两种命令,set 一般和 doc Cooperate with query primary key and update,不能和where 配合,update 可以和 doc / where 配合.
Due to the abovejson对象里,无法通过doc Get a specific field in it,所以我们用 where 和 update to check for updates.

for (let i = 0; i < newwords.length; i++) {
       // forUpdate a single piece of data in a loop
      await db.collection('book_words')
        .where({
    
          book_id: event.book_id,
          "book_words.unit_id": event.unit_id,
          "book_words.list.word": event.newwords[i].word
        })
        .update({
    
          data: {
    
            ['book_words.'+(event.unit_id-1)+'.list.'+(event.newwords[i].index)+'.checked']: true
          }
        })
        .then((res) => {
    
          console.log("update book_words result", res)
        })
        .catch(err => {
    
          console.error(err)
        })
  }

解释：

a. where

"book_words.unit_id" ：match elements in an array,文档：查询、更新数组/嵌套对象

也可以用 elemMatch 来查询元素：
文档：Command.elemMatch

const db = cloud.database();
const _ = db.command;  // command命令

//......function
.where({
    
          book_id: event.book_id,
          book_words:_.elemMatch({
    
            unit_id: event.unit_id,
            list:_.elemMatch({
    
              word: event.newwords[i].word
            })
          })
        })

b. update

[文档：查询、更新数组/嵌套对象]
(https://developers.weixin.qq.com/miniprogram/dev/wxcloud/guide/database/query-array-object.html)
.
['book_words.'+(event.unit_id-1)+'.list.'+(event.newwords[i].index)+'.checked'] ：
相当于：book_words.0.list.0.checked -> book_words[0].list[0].checked
.+number = find arraynumber项元素,
更新checked值.
.

2. 添加,Update if any,没有则添加

add array to database,有则更新,无则添加,需要用到 set 命令,
update : 更新一条记录;
set : 更新替换一条记录.
文档：更新记录
文档：增删查改SDK-更新

 // doc 会自动将 word 设为主键ID ,When inserted, it will be based on 主键word 判断是更新还是新增;
 // 同样在forBatch single addition in loop
 for (let i = 0; i < newwords.length; i++) {
      
      await db.collection('new_words').doc(event.newwords[i].word).set({
    
          data: event.newwords[i]
        }).then((res) => {
    
          console.log("new_words update result", res)
        })
        .catch(err => {
    
          console.error("new_words", err)
        });
  }

The official documentation of the WeChat applet is too confusing,A hammer in the east A hammer in the west,Artificially making simple things more difficult,So write this blog to record.以供参考.