package errors

import "errors"

Package errors implements functions to manipulate errors.

Example

Code:play  

package main

import (
	"fmt"
	"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 main() {
	if err := oops(); err != nil {
		fmt.Println(err)
	}
}

Output:

1989-03-15 22:30:00 +0000 UTC: the file system has gone away

Index

Examples

Functions

func As 

func As(err error, target interface{}) bool

As finds the first error in err's chain that matches target, and if so, sets target to that error value and returns true.

An error matches target if the error's concrete value is assignable to the value pointed to by target, or if the error has a method As(interface{}) bool such that As(target) returns true. In the latter case, the As method is responsible for setting target.

As will panic if target is not a non-nil pointer to either a type that implements error, or to any interface type. As returns false if err is nil.

Example

Code:play  

package main

import (
	"errors"
	"fmt"
	"os"
)

func main() {
	if _, err := os.Open("non-existing"); err != nil {
		var pathError *os.PathError
		if errors.As(err, &pathError) {
			fmt.Println("Failed at path:", pathError.Path)
		} else {
			fmt.Println(err)
		}
	}

}

Output:

Failed at path: non-existing

func Is 

func Is(err, target error) bool

Is reports whether any error in err's chain matches target.

An error is considered to match a target if it is equal to that target or if it implements a method Is(error) bool such that Is(target) returns true.

func New 

func New(text string) error

New returns an error that formats as the given text.

Example

Code:play  

package main

import (
	"errors"
	"fmt"
)

func main() {
	err := errors.New("emit macho dwarf: elf header corrupted")
	if err != nil {
		fmt.Print(err)
	}
}

Output:

emit macho dwarf: elf header corrupted
Example (Errorf)

The fmt package's Errorf function lets us use the package's formatting features to create descriptive error messages.

Code:play  

package main

import (
	"fmt"
)

func main() {
	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 Unwrap 

func Unwrap(err error) error

Unwrap returns the result of calling the Unwrap method on err, if err's type contains an Unwrap method returning error. Otherwise, Unwrap returns nil.

Source Files

errors.go wrap.go

Version
v1.13.0-beta.1
Published
Jun 26, 2019
Platform
js/wasm
Imports
1 packages
Last checked
44 seconds ago –

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