Go语言中创建结构体切片并与MongoDB数据映射的实践指南

package main

import "fmt"

func main() {
    // 创建一个包含3个map[string]string的数组
    // 必须为每个map元素调用make进行初始化
    maps := [3]map[string]string{
        make(map[string]string),
        make(map[string]string),
        make(map[string]string),
    }

    // 赋值示例
    maps[0]["name"] = "Alice"
    maps[0]["time"] = "2023-01-01"
    maps[0]["qty"] = "10" // 注意：这里qty是字符串，与MongoDB schema中的int类型不符

    maps[1]["name"] = "Bob"
    maps[1]["time"] = "2023-01-02"
    maps[1]["qty"] = "5"

    fmt.Println(maps)
    // 输出: [map[name:Alice qty:10 time:2023-01-01] map[name:Bob qty:5 time:2023-01-02] map[]]
}

package main

import "fmt"

func main() {
    // 创建一个长度为3的map[string]string切片
    // 此时切片中的3个map元素都是nil
    maps := make([]map[string]string, 3)

    // 必须迭代切片并初始化每个map元素
    for i := range maps {
        maps[i] = make(map[string]string)
    }

    // 现在可以安全地赋值
    maps[0]["name"] = "Charlie"
    maps[0]["time"] = "2023-03-01"
    maps[0]["qty"] = "7"

    fmt.Println(maps)
    // 输出: [map[name:Charlie qty:7 time:2023-03-01] map[] map[]]
}

[   
  {
    "name":"sample",
    "time": "2014-04-05",
    "Qty":3
  },
  {
   "name":"sample",
   "time": "2014-04-05",
   "Qty":3
  }
]

package main

import (
    "fmt"
    "time" // 假设time字段存储为time.Time类型
)

// Item 结构体定义，用于映射MongoDB文档
// `bson:"fieldName"` 标签用于指定Go结构体字段与MongoDB文档字段的映射关系
type Item struct {
    Name string    `bson:"name"` // 映射到MongoDB的"name"字段
    Time time.Time `bson:"time"` // 映射到MongoDB的"time"字段
    Qty  int       `bson:"qty"`  // 映射到MongoDB的"Qty"字段
}

func main() {
    // 创建一个Item结构体切片
    // 通常我们不需要预先设定大小，而是动态添加
    var items []Item 

    // 创建并添加第一个Item
    item1 := Item{
        Name: "sample",
        Time: time.Date(2014, time.April, 5, 0, 0, 0, 0, time.UTC),
        Qty:  3,
    }
    items = append(items, item1)

    // 创建并添加第二个Item
    item2 := Item{
        Name: "another_sample",
        Time: time.Date(2014, time.April, 6, 0, 0, 0, 0, time.UTC),
        Qty:  5,
    }
    items = append(items, item2)

    fmt.Printf("Items: %+v\n", items)
    // 输出示例: Items: [{Name:sample Time:2014-04-05 00:00:00 +0000 UTC Qty:3} {Name:another_sample Time:2014-04-06 00:00:00 +0000 UTC Qty:5}]

    // 如果需要固定大小的结构体数组，可以这样声明和初始化
    var fixedItems [2]Item
    fixedItems[0] = Item{
        Name: "fixed_sample_1",
        Time: time.Date(2023, time.January, 1, 0, 0, 0, 0, time.UTC),
        Qty:  10,
    }
    fixedItems[1] = Item{
        Name: "fixed_sample_2",
        Time: time.Date(2023, time.January, 2, 0, 0, 0, 0, time.UTC),
        Qty:  20,
    }
    fmt.Printf("Fixed Items: %+v\n", fixedItems)
    // 输出示例: Fixed Items: [{Name:fixed_sample_1 Time:2023-01-01 00:00:00 +0000 UTC Qty:10} {Name:fixed_sample_2 Time:2023-01-02 00:00:00 +0000 UTC Qty:20}]
}