cancelable

Documentation

Overview

Package cancelable provides a cancelable version of io.Closer.

This is intended to be used by functions where the responsibility for closing a resource sometimes belongs to the function itself (e.g. early returns due to error handling), and sometimes belongs to the caller.

Index

• type Closer
  • func NewCloser(c io.Closer) *Closer
  • func (c *Closer) Cancel()
  • func (c *Closer) Close() error

Examples

• Closer

Types

type Closer

type Closer struct {
	// contains filtered or unexported fields
}

Closer is an io.Closer that can be cancelled.

Example

package main

import (
	"fmt"

	"github.com/samuong/alpaca/cancelable"
)

type printCloser struct {
	msg string
}

// Close prints the printCloser's msg on stdout.
func (pc *printCloser) Close() error {
	fmt.Printf("Close() called: %s\n", pc.msg)
	return nil
}

func main() {
	c := create(false) // defer in create() prints once
	c.Close()          // prints again

	c = create(true) // defer cancelled, no print
	c.Close()        // prints

}

func create(doCancel bool) *printCloser {
	pc := &printCloser{fmt.Sprintf("doCancel: %v", doCancel)}

	closer := cancelable.NewCloser(pc)
	defer closer.Close()

	if !doCancel {
		return pc // deferred Close will cause msg to be printed
	}

	closer.Cancel() // Cancel will prevent Close being called from defer
	return pc
}

Output:

Close() called: doCancel: false
Close() called: doCancel: false
Close() called: doCancel: true

func NewCloser

func NewCloser(c io.Closer) *Closer

NewCloser returns a cancelable.Closer that wraps an io.Closer.

func (*Closer) Cancel

func (c *Closer) Cancel()

Cancel turns any future calls to Close into a no-op.

func (*Closer) Close

func (c *Closer) Close() error

Close calls the Close function on the io.Closer (if it has not been cancelled or already closed). It is safe to call this multiple times.