Json绑定用于Postgres数据库的Golang中的枚举类型值

Question

I am implementing a rest api where I send a json request body.

type Service struct {
    id int64 `db:"id" json:"id"`
    Name string `form:"name" db:"name" json:"name" binding:"required"`
    Servicetype string `form:"type"  db:"type" json:"type" binding:"required"`
}

func myHandler(c *gin.Context) {
    if c.BindJSON(&json) == nil {
        fmt.Println(json.Servicetype)
    } else {
         fmt.Println("json binding error")
    }
}

Servicetype is of type enum in my database. How can I have binding for that in my Service struct? I am able to bind the Name field as it is of type VARCHAR in database. But it fails to bind when I add Servicetype in the struct. I am using postgres as my database.

Answer 1

Servicetype must implement Scanner and Valuer interfaces.

Take a look on how std package does it for NullString

// NullString represents a string that may be null.
// NullString implements the Scanner interface so
// it can be used as a scan destination:


type NullString struct {
    String string
    Valid  bool // Valid is true if String is not NULL
}

// Scan implements the Scanner interface.
func (ns *NullString) Scan(value interface{}) error {
    if value == nil {
        ns.String, ns.Valid = "", false
        return nil
    }
    ns.Valid = true
    return convertAssign(&ns.String, value)
}

// Value implements the driver Valuer interface.
func (ns NullString) Value() (driver.Value, error) {
    if !ns.Valid {
        return nil, nil
    }
    return ns.String, nil
}