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// Copyright 2012 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package errors_test
import (
"errors"
"fmt"
"io/fs"
"os"
"time"
)
// MyError is an error implementation that includes a time and message.
type MyError struct {
When time.Time
What string
}
func (e MyError) Error() string {
return fmt.Sprintf("%v: %v", e.When, e.What)
}
func oops() error {
return MyError{
time.Date(1989, 3, 15, 22, 30, 0, 0, time.UTC),
"the file system has gone away",
}
}
func Example() {
if err := oops(); err != nil {
fmt.Println(err)
}
// Output: 1989-03-15 22:30:00 +0000 UTC: the file system has gone away
}
func ExampleNew() {
err := errors.New("emit macho dwarf: elf header corrupted")
if err != nil {
fmt.Print(err)
}
// Output: emit macho dwarf: elf header corrupted
}
// The fmt package's Errorf function lets us use the package's formatting
// features to create descriptive error messages.
func ExampleNew_errorf() {
const name, id = "bimmler", 17
err := fmt.Errorf("user %q (id %d) not found", name, id)
if err != nil {
fmt.Print(err)
}
// Output: user "bimmler" (id 17) not found
}
func ExampleJoin() {
err1 := errors.New("err1")
err2 := errors.New("err2")
err := errors.Join(err1, err2)
fmt.Println(err)
if errors.Is(err, err1) {
fmt.Println("err is err1")
}
if errors.Is(err, err2) {
fmt.Println("err is err2")
}
// Output:
// err1
// err2
// err is err1
// err is err2
}
func ExampleIs() {
if _, err := os.Open("non-existing"); err != nil {
if errors.Is(err, fs.ErrNotExist) {
fmt.Println("file does not exist")
} else {
fmt.Println(err)
}
}
// Output:
// file does not exist
}
func ExampleAs() {
if _, err := os.Open("non-existing"); err != nil {
var pathError *fs.PathError
if errors.As(err, &pathError) {
fmt.Println("Failed at path:", pathError.Path)
} else {
fmt.Println(err)
}
}
// Output:
// Failed at path: non-existing
}
func ExampleUnwrap() {
err1 := errors.New("error1")
err2 := fmt.Errorf("error2: [%w]", err1)
fmt.Println(err2)
fmt.Println(errors.Unwrap(err2))
// Output
// error2: [error1]
// error1
}
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