fed notes

Appearance

错误处理 ​

https://gobyexample-cn.github.io/errors

基础用法

go
func f1(arg int) (int, error) {
    if arg == 42 {

        return -1, errors.New("can't work with 42")

    }

    return arg + 3, nil
}

自定义错误：

go
type argError struct {
    arg  int
    prob string
}

func (e *argError) Error() string {
    return fmt.Sprintf("%d - %s", e.arg, e.prob)
}

func f2(arg int) (int, error) {
    if arg == 42 {

        return -1, &argError{arg, "can't work with it"}
    }
    return arg + 3, nil
}

只要有 Error() string 就可以

go
func main() {

    for _, i := range []int{7, 42} {
        if r, e := f1(i); e != nil {
            fmt.Println("f1 failed:", e)
        } else {
            fmt.Println("f1 worked:", r)
        }
    }

    for _, i := range []int{7, 42} {
        if r, e := f2(i); e != nil {
            fmt.Println("f2 failed:", e)
        } else {
            fmt.Println("f2 worked:", r)
        }
    }

    // 类型断言
    _, e := f2(42)
    if ae, ok := e.(*argError); ok {
        fmt.Println(ae.arg)
        fmt.Println(ae.prob)
    }
}