错误基础 #

type error interface {
    Error() string
}

import "errors"

err := errors.New("something went wrong")

err := fmt.Errorf("failed to open file: %s", filename)

result, err := someFunction()
if err != nil {
    return err
}

if err != nil {
    fmt.Println("Error:", err)
}

func doSomething() error {
    if err := step1(); err != nil {
        return err
    }
    
    if err := step2(); err != nil {
        return err
    }
    
    return nil
}

func readFile(path string) ([]byte, error) {
    data, err := os.ReadFile(path)
    if err != nil {
        return nil, err
    }
    return data, nil
}

func processFile(path string) error {
    data, err := os.ReadFile(path)
    if err != nil {
        return fmt.Errorf("failed to read %s: %w", path, err)
    }
    return nil
}

func openFile(path string) (*os.File, error) {
    f, err := os.Open(path)
    if err != nil {
        return nil, fmt.Errorf("open file: %w", err)
    }
    return f, nil
}

func fetch(url string) ([]byte, error) {
    resp, err := http.Get(url)
    if err != nil {
        return nil, fmt.Errorf("fetch %s: %w", url, err)
    }
    defer resp.Body.Close()
    
    if resp.StatusCode != http.StatusOK {
        return nil, fmt.Errorf("status %d", resp.StatusCode)
    }
    
    return io.ReadAll(resp.Body)
}

func queryUser(db *sql.DB, id int) (*User, error) {
    row := db.QueryRow("SELECT id, name FROM users WHERE id = ?", id)
    
    var user User
    err := row.Scan(&user.ID, &user.Name)
    if err != nil {
        if err == sql.ErrNoRows {
            return nil, fmt.Errorf("user %d not found", id)
        }
        return nil, fmt.Errorf("query user: %w", err)
    }
    
    return &user, nil
}

func process(data []byte) error {
    if len(data) == 0 {
        return errors.New("empty data")
    }
    
    // 处理...
    return nil
}

if err != nil {
    return fmt.Errorf("operation failed: %w", err)
}

// 不好
data, _ := os.ReadFile(path)

// 好
data, err := os.ReadFile(path)
if err != nil {
    return err
}