go语⾔array_column⽅法（反射+泛型）php 的 array_column 太太太⽅便了，实现了⼀款 go 语⾔版本供借鉴～
功能1：提取 []struct 中 column 列。desk中存储为 slice
功能2：提取 []struct 中的 index 列作为 key，column列作为值。 desk 中存储为map
参数说明 :
@param desk [slice|map] 指针类型，⽅法最终的存储位置
@param input []struct，待转换的结构体切⽚
@param columnKey string
@param indexKey string
go语⾔代码实现：
package array_column_test
import (
"reflect"
"fmt"
"errors"
)
func StructColumn(desk, input interface{}, columnKey, indexKey string) (err error) {
deskValue := reflect.ValueOf(desk)
if deskValue.Kind() != reflect.Ptr {
return errors.New("desk must be ptr")
}
rv := reflect.ValueOf(input)
if rv.Kind() != reflect.Slice && rv.Kind() != reflect.Array {
return errors.New("input must be map slice or array")
}
rt := reflect.TypeOf(input)
if rt.Elem().Kind() != reflect.Struct {
return errors.New("input's elem must be struct")
}
if len(indexKey) > 0 {
return structIndexColumn(desk, input, columnKey, indexKey)
}
return structColumn(desk, input, columnKey)
}
func structColumn(desk, input interface{}, columnKey string) (err error) {
if len(columnKey) == 0 {
return errors.New("columnKey cannot not be empty")
}
deskElemType := reflect.TypeOf(desk).Elem()
if deskElemType.Kind() != reflect.Slice {
return errors.New("desk must be slice")
}
rv := reflect.ValueOf(input)
rt := reflect.TypeOf(input)
var columnVal reflect.Value
deskValue := reflect.ValueOf(desk)
direct := reflect.Indirect(deskValue)
for i := 0; i < rv.Len(); i++ {
columnVal, err = findStructValByColumnKey(rv.Index(i), rt.Elem(), columnKey)
if err != nil {
return
}
if deskElemType.Elem().Kind() != columnVal.Kind() {
return errors.New(fmt.Sprintf("your slice must be []%s", columnVal.Kind()))
}
direct.Set(reflect.Append(direct, columnVal))
}
return
}
func findStructValByColumnKey(curVal reflect.Value, elemType reflect.Type, columnKey string) (columnVal reflect.Value, err error) {
columnExist := false
for i := 0; i < elemType.NumField(); i++ {
curField := curVal.Field(i)
if elemType.Field(i).Name == columnKey {
columnExist = true
columnVal = curField
continue
}
}
if !columnExist {
return columnVal, errors.New(fmt.Sprintf("columnKey %s not found in %s's field", columnKey, elemType))
}
return
}
func structIndexColumn(desk, input interface{}, columnKey, indexKey string) (err error) {
deskValue := reflect.ValueOf(desk)
if deskValue.Elem().Kind() != reflect.Map {
return errors.New("desk must be map")
}
deskElem := deskValue.Type().Elem()
if len(columnKey) == 0 && deskElem.Elem().Kind() != reflect.Struct {
return errors.New(fmt.Sprintf("desk's elem expect struct, got %s", deskElem.Elem().Kind()))
}
rv := reflect.ValueOf(input)
rt := reflect.TypeOf(input)
elemType := rt.Elem()
var indexVal, columnVal reflect.Value
direct := reflect.Indirect(deskValue)
mapReflect := reflect.MakeMap(deskElem)
deskKey := deskValue.Type().Elem().Key()
for i := 0; i < rv.Len(); i++ {
curVal := rv.Index(i)
indexVal, columnVal, err = findStructValByIndexKey(curVal, elemType, indexKey, columnKey)
if err != nil {
return
}
if deskKey.Kind() != indexVal.Kind() {
return errors.New(fmt.Sprintf("cant't convert %s to %s, your map'key must be %s", indexVal.Kind(), deskKey.Kind(), indexVal.Kind()))
typeof array
}
if len(columnKey) == 0 {
mapReflect.SetMapIndex(indexVal, curVal)
direct.Set(mapReflect)
} else {
if deskElem.Elem().Kind() != columnVal.Kind() {
return errors.New(fmt.Sprintf("your map must be map[%s]%s", indexVal.Kind(), columnVal.Kind()))
}
mapReflect.SetMapIndex(indexVal, columnVal)
direct.Set(mapReflect)
}
}
return
}
func findStructValByIndexKey(curVal reflect.Value, elemType reflect.Type, indexKey, columnKey string) (indexVal, columnVal reflect.Value, err error) {    indexExist := false
columnExist := false
for i := 0; i < elemType.NumField(); i++ {
curField := curVal.Field(i)
if elemType.Field(i).Name == indexKey {
switch curField.Kind() {
case reflect.String, reflect.Int64, reflect.Int32, reflect.Int16, reflect.Int8, reflect.Int, reflect.Float64, reflect.Float32:
indexExist = true
indexVal = curField
default:
return indexVal, columnVal, errors.New("indexKey must be int float or string")
}
}
if elemType.Field(i).Name == columnKey {
columnExist = true
columnVal = curField
continue
}
}
if !indexExist {
return indexVal, columnVal, errors.New(fmt.Sprintf("indexKey %s not found in %s's field", indexKey, elemType))
}
if len(columnKey) > 0 && !columnExist {
return indexVal, columnVal, errors.New(fmt.Sprintf("columnKey %s not found in %s's field", columnKey, elemType))    }
return
}
测试
func TestBindFromArrayColumn(t *testing.T) {
user1 := User{
ID:  1,
NAME: "zwk",
}
user2 := User{
ID:  2,
NAME: "zzz",
}
var list3 []User
list3 = append(list3, user1)
list3 = append(list3, user2)
var userMap map[int]string
StructColumn(&userMap, list3, "NAME", "ID")
fmt.Printf("%#v\n", userMap)
var userMap1 map[int]User
StructColumn(&userMap1, list3, "", "ID")
fmt.Printf("%#v\n", userMap1)
var userSlice []int
StructColumn(&userSlice, list3, "ID", "")
fmt.Printf("%#v\n", userSlice)
}
测试结果
map[int]string{1:"zwk", 2:"zzz"}
map[int]User{1:User{ID:1, NAME:"zwk"}, 2:User{ID:2, NAME:"zzz"}}
[]int{1, 2}

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