使用自定义扫描功能汇总枚举类型
我正在尝试删除性别类型，该枚举只是hood下的int64（我不想使用此类型的任何字符串表示形式）。
问题是性别价值无法正确处理，我总是以0结尾。
我缺少一些东西，但我看不到它...
非常感谢。
https://go.dev/play/pplay/p/bfni_espzjy
package main
import (
"database/sql"
"encoding/json"
"fmt"
)
type Person struct {
name string `json:"name"`
gender Gender `json:"gender"`
}
type Gender int64
const (
Undefined Gender = iota
Male
Female
NonBinary
)
func (g *Gender) Scan(v interface{}) error {
if v == nil {
*g = Gender(Undefined)
return nil
}
ns := sql.NullInt64{}
if err := ns.Scan(v); err != nil {
return err
}
if !ns.Valid {
return fmt.Errorf("Gender.Scan: column is not nullable")
}
if ns.Int64 > 3 {
return fmt.Errorf("Gender.Scan: gender value > 3")
}
*g = genderFromInt64(ns.Int64) // tried Gender(ns.Int64) without success
return nil
}
// tried genderFromInt64(i int64) instead of Gender(ns.Int64) without success
func genderFromInt64(i int64) Gender {
switch i {
case 0:
return Undefined
case 1:
return Male
case 2:
return Female
case 3:
return NonBinary
default:
return Female
}
}
// Value() is not used yet
func (g Gender) Value() (driver.Value, error) {
return int64(g), nil
}
func (g Gender) String() string {
return [...]string{"Undefined", "Male", "Female", "Non-binary"}[g]
}
func main() {
var person Person
jsonPerson := `{"name": "John", "gender": 2}`
json.Unmarshal([]byte(jsonPerson), &person)
fmt.Printf("%+v", person)
}
I'm trying to unmarshall a Gender type that is an Enumeration that is just int64 under the hood (I don't want to use any string representation of this type).
Problem is that the Gender value is not handled properly, I always ended with 0.
I'm missing something but I don't see it...
Thank you so much.
https://go.dev/play/p/bfnI_ESpzJY
package main
import (
"database/sql"
"encoding/json"
"fmt"
)
type Person struct {
name string `json:"name"`
gender Gender `json:"gender"`
}
type Gender int64
const (
Undefined Gender = iota
Male
Female
NonBinary
)
func (g *Gender) Scan(v interface{}) error {
if v == nil {
*g = Gender(Undefined)
return nil
}
ns := sql.NullInt64{}
if err := ns.Scan(v); err != nil {
return err
}
if !ns.Valid {
return fmt.Errorf("Gender.Scan: column is not nullable")
}
if ns.Int64 > 3 {
return fmt.Errorf("Gender.Scan: gender value > 3")
}
*g = genderFromInt64(ns.Int64) // tried Gender(ns.Int64) without success
return nil
}
// tried genderFromInt64(i int64) instead of Gender(ns.Int64) without success
func genderFromInt64(i int64) Gender {
switch i {
case 0:
return Undefined
case 1:
return Male
case 2:
return Female
case 3:
return NonBinary
default:
return Female
}
}
// Value() is not used yet
func (g Gender) Value() (driver.Value, error) {
return int64(g), nil
}
func (g Gender) String() string {
return [...]string{"Undefined", "Male", "Female", "Non-binary"}[g]
}
func main() {
var person Person
jsonPerson := `{"name": "John", "gender": 2}`
json.Unmarshal([]byte(jsonPerson), &person)
fmt.Printf("%+v", person)
}
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评论（1）
在您的代码中，我想指出两件事（@Mkopriva已经提到）
人的字段是未伸出的，并且对unmarshal方法看不到。您可以使用
Go Vet命令它将帮助您防止这些错误您已经实现了将性别价值从枚举转换为字符串的Stringer接口。如果您不想将此类型表示为字符串，则可以注释
字符串方法func（g gender）string（）字符串{return [...]字符串{“ undefined”，“ male”，“ heapen”，“ nont binary”} [g]}>https://go.dev/play/p/c1zuv_fes0k
In your code, I want to point out 2 things (which is already mention by @mkopriva)
Person's fields are unexported and are not visible to unmarshal methods. You can use
go vetcommand it will help you to prevent these kinds of errorsYou have implemented the Stringer interface which converts Gender value from enum to string. if you don't want to represent this type as a string you can comment
Stringmethodfunc (g Gender) String() string { return [...]string{"Undefined", "Male", "Female", "Non-binary"}[g] }https://go.dev/play/p/C1ZUv_fES0k