Golang使用errors包封装与链式调用实践

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

if errors.Is(err, os.ErrNotExist) {
    log.Println("config file not found")
}

var pathErr *os.PathError
if errors.As(err, &pathErr) {
    log.Printf("file operation failed on path: %s", pathErr.Path)
}
</font>
<p>这两个函数会自动遍历错误链，无需手动解包。</p>
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<H3>自定义错误类型与链式调用实践</H3>
<p>在业务中，常需定义自己的错误类型。只要实现 Unwrap 方法，就能参与错误链。</p>
<font face="monospace">
<pre class="brush:php;toolbar:false;">type MyError struct {
    Msg string
    Err error
}

func (e *MyError) Error() string {
    return e.Msg
}

func (e *MyError) Unwrap() error {
    return e.Err
}

err := fmt.Errorf("higher level failed: %w", &MyError{
    Msg: "IO failed",
    Err: os.ErrPermission,
})