Golang自定义错误类型实现与应用示例

type MyError struct {
    Code    int
    Message string
    Err     error // 可选：包装底层错误
}

func (e *MyError) Error() string {
    if e.Err != nil {
        return fmt.Sprintf("[%d] %s: %v", e.Code, e.Message, e.Err)
    }
    return fmt.Sprintf("[%d] %s", e.Code, e.Message)
}

func NewValidationError(msg string) *MyError {
    return &MyError{
        Code:    400,
        Message: "validation failed: " + msg,
    }
}

func NewDatabaseError(originalErr error) *MyError {
    return &MyError{
        Code:    500,
        Message: "database operation failed",
        Err:     originalErr,
    }
}

func ProcessUserInput(input string) error {
    if input == "" {
        return NewValidationError("input cannot be empty")
    }

    err := database.Save(input)
    if err != nil {
        return NewDatabaseError(err)
    }

    return nil
}

err := ProcessUserInput("")
if err != nil {
    var myErr *MyError
    if errors.As(err, &myErr) {
        switch myErr.Code {
        case 400:
            log.Printf("Client error: %s", myErr.Message)
        case 500:
            log.Printf("Server error: %s", myErr.Message)
        }
    } else {
        log.Printf("Unknown error: %v", err)
    }
}

if err := readFile(); err != nil {
    return fmt.Errorf("failed to read config: %w", NewValidationError("file missing"))
}