<p>import "errors"
import "fmt"
By convention, errors are the last return value and have type error, a built-in interface.
func f1(arg int) (int, error) {
if arg == 42 {
errors.New constructs a basic error value with the given error message.
return -1, errors.New("can't work with 42")
}
A nil value in the error position indicates that there was no error.
return arg + 3, nil
}
It’s possible to use custom types as errors by implementing the Error() method on them. Here’s a variant on the example above that uses a custom type to explicitly represent an argument error.
type argError struct {
arg int
prob string
}
func (e <em>argError) Error() string {
return fmt.Sprintf("%d - %s", e.arg, e.prob)
}
func f2(arg int) (int, error) {
if arg == 42 {
In this case we use &argError syntax to build a new struct, supplying values for the two fields arg and prob.
return -1, &argError{arg, "can't work with it"}
}
return arg + 3, nil
}
func main() {
The two loops below test out each of our error-returning functions. Note that the use of an inline error check on the if line is a common idiom in Go code.
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)
}
}
If you want to programmatically use the data in a custom error, you’ll need to get the error as an instance of the custom error type via type assertion.
_, e := f2(42)
if ae, ok := e.(</em>argError); ok {
fmt.Println(ae.arg)
fmt.Println(ae.prob)
}
}</p>
<hr/>**评论：**<br/><br/>SilverWingedSeraph: <pre><p>Please use Pastebin, GitHub Gist, or at least proper Reddit formatting, so we can actually read your code.</p></pre>saturn_vk: <pre><p>Rather, just use play.golang.org</p></pre>shovelpost: <pre><p>It seems you have copy pasted the code (and the text) from <a href="https://gobyexample.com/errors" rel="nofollow">this page</a>.</p>
<p>The page text (on the left) explains very well what each part of the code (on the right) does. What exactly is it that you do not understand?</p></pre>
