json绑定postgres数据库的golang中的枚举类型值(Json binding for enum type values in golang for postgres database)

Servicetype must implement Scanner and Valuer interfaces.

// 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
}