在 Go 中按子数组值对切片进行分组

Question

我有一个子数组，格式如下

我想根据每个子数组中的 unit_type_name 字段将其分组到一个新的切片中。

如何按 unit_type_name 对切片进行分组？是否有任何本机 Go 函数可用于执行此操作？如果我循环上面的内容，那么我将得到一个重复的，我怎样才能避免这种情况？

Answer 1

我认为 Go 没有内置功能可以帮助你做到这一点（我可能是错的）。我的假设是 PHP 数组将转换为 JSON 对象。我设法得到下面的代码来帮助你根据 unit_type_name 对数组（JSON 格式）进行排序我创建了两个结构，它们具有 JSON 类似于数组键的值

//StandardType ...
type StandardType struct {
    UnitID                int    `json:"unit_id"`
    IsFormal              int    `json:"is_formal"`
    AssignmentName        string `json:"assignment_name"`
    AssignmentDescription string `json:"assignment_description"`
    StandardID            int    `json:"standard_id"`
    StandardName          string `json:"standard_name"`
    StandardDescription   string `json:"standard_description"`
}

//AutoGenerated ...
type AutoGenerated struct {
    UnitID                int            `json:"unit_id"`
    AssignmentName        string         `json:"assignment_name"`
    AssignmentDescription string         `json:"assignment_description"`
    AssignmentTotalScore  int            `json:"assignment_total_score"`
    UnitTypeName          string         `json:"unit_type_name"`
    IsGraded              int            `json:"is_graded"`
    StandardID            int            `json:"standard_id"`
    ScoringType           string         `json:"scoring_type"`
    AttemptScore          int            `json:"attempt_score"`
    UnitDuedate           string         `json:"unit_duedate"`
    Standard              []StandardType `json:"standard"`
}
var jsonData = ``
func main() { 
    m := []AutoGenerated{}
    err := json.Unmarshal([]byte(jsonData), &m)
    if err != nil {
        panic(err)
    }

我创建了一个地图来放置 unit_type_name 键

    sliceKeys := make(map[string]string)

我还创建了映射以保存在自动生成数组中具有相似 unit_type_name 键的数组

    groupedSlices := make(map[string][]AutoGenerated)

然后我遍历解码的 JSON 字符串搜索 unit_type_name

    for i := range m {

如果键切片中已经存在 unit_type_name 我将数组项添加到组切片中

      if _, ok := sliceKeys[m[i].UnitTypeName]; ok {
        autogenerated := groupedSlices[m[i].UnitTypeName]
        autogenerated = append(autogenerated, m[i])
        groupedSlices[m[i].UnitTypeName] = autogenerated
      } else {

否则我会创建一个新的数组键并将项目添加到其中

        sliceKeys[m[i].UnitTypeName] = m[i].UnitTypeName
        autogenerated := []AutoGenerated{}
        autogenerated = append(autogenerated, m[i])
        groupedSlices[m[i].UnitTypeName] = autogenerated
     }
  }
  fmt.Println(sliceKeys)
  fmt.Println(groupedSlices)
}

输入：

[{"unit_id": 6504,"assignment_name": "Grade assignment","assignment_description": "","assignment_total_score": 10,"unit_type_name": "Homework","is_graded": 1,"standard_id": 1219,
"scoring_type": "score","attempt_score": 8,"unit_duedate": "2016-02-10 09:00:00",
"standard": [{"unit_id": 6504,"is_formal": 1,"assignment_name": "Grade assignment","assignment_description": "",
"standard_id": 1220,"standard_name": "9-10.RL.3","standard_description": "Analyze how complex characters (e.g., those with multiple or conflicting motivations) develop over the course of a "
}]},{"unit_id": 6504,"assignment_name": "Grade assignment","assignment_description": "","assignment_total_score": 10,
"unit_type_name": "Paper","is_graded": 1,"standard_id": 1219,"scoring_type": "score","attempt_score": 8,"unit_duedate": "2016-02-10 09:00:00","standard": [{"unit_id": 6504,"is_formal": 1,"assignment_name": "Grade assignment","assignment_description": "","standard_id": 1220,"standard_name": "9-10.RL.3","standard_description": "Analyze how complex characters (e.g., those with multiple or conflicting motivations) develop over the course of a "}]},{
"unit_id": 6504,"assignment_name": "Grade assignment","assignment_description": "",
"assignment_total_score": 10,"unit_type_name": "Aything else","is_graded": 1,"standard_id": 1219,
"scoring_type": "score","attempt_score": 8,"unit_duedate": "2016-02-10 09:00:00","standard": [{
"unit_id": 6504,"is_formal": 1,"assignment_name": "Grade assignment","assignment_description": "","standard_id": 1220,
"standard_name": "9-10.RL.3","standard_description": "Analyze how complex characters (e.g., those with multiple or conflicting motivations) develop over the course of a "}]}]

输出：

map[Homework:Homework Paper:Paper Aything else:Aything else]

map[
Homework:[
{6504 Grade assignment  10 Homework 1 1219 score 8 2016-02-10 09:00:00 [{6504 1 Grade assignment  1220 9-10.RL.3 Analyze how complex characters (e.g., those with multiple or conflicting motivations) develop over the course of a }]}
] 

Paper:[
{6504 Grade assignment  10 Paper 1 1219 score 8 2016-02-10 09:00:00 [{6504 1 Grade assignment  1220 9-10.RL.3 Analyze how complex characters (e.g., those with multiple or conflicting motivations) develop over the course of a }]}
] 

Aything else:[
{6504 Grade assignment  10 Aything else 1 1219 score 8 2016-02-10 09:00:00 [{6504 1 Grade assignment  1220 9-10.RL.3 Analyze how complex characters (e.g., those with multiple or conflicting motivations) develop over the course of a }]}]

]

Answer 2

这是我写的一个通用的 GroupBy 函数：

// Created by BaiJiFeiLong@gmail.com at 2021/8/27 10:51
package main

import (
    "fmt"
    "reflect"
    "strconv"
)

func GroupBy(arr interface{}, groupFunc interface{}) interface{} {
    groupMap := reflect.MakeMap(reflect.MapOf(reflect.TypeOf(groupFunc).Out(0), reflect.TypeOf(arr)))
    for i := 0; i < reflect.ValueOf(arr).Len(); i++ {
        groupPivot := reflect.ValueOf(groupFunc).Call([]reflect.Value{reflect.ValueOf(arr).Index(i)})[0]
        if !groupMap.MapIndex(groupPivot).IsValid() {
            groupMap.SetMapIndex(groupPivot, reflect.MakeSlice(reflect.SliceOf(reflect.TypeOf(arr).Elem()), 0, 0))
        }
        groupMap.SetMapIndex(groupPivot, reflect.Append(groupMap.MapIndex(groupPivot), reflect.ValueOf(arr).Index(i)))
    }
    return groupMap.Interface()
}

func main() {
    fmt.Println(GroupBy([]int{1, 22, 3, 44, 555}, func(value int) string {
        return strconv.Itoa(len(strconv.Itoa(value)))
    }))
}

输出：

map[1:[1 3] 2:[22 44] 3:[555]]

对于你的问题，应该是这样的代码：

group := GroupBy(items, func(item Item) string {
    return item.UnitTypeName
}).(map[string][]Item)

在 Go 中按子数组值对切片进行分组

Group slice by subarray values in Go

go

slice