notifier

Documentation

Overview

Package notifier provides a simple notification dispatcher meant to be embedded in larger structures who wish to allow clients to sign up for event notifications.

Index

• type Notifiee
• type Notifier
  • func RateLimited(limit int) *Notifier
  • func (n *Notifier) Notify(e Notifiee)
  • func (n *Notifier) NotifyAll(notify func(Notifiee))
  • func (n *Notifier) StopNotify(e Notifiee)

Types

type Notifiee

type Notifiee interface{}

Notifiee is a generic interface. Clients implement their own Notifiee interfaces to ensure type-safety of notifications:

type RocketNotifiee interface{
  Countdown(r Rocket, countdown time.Duration)
  LiftedOff(Rocket)
  ReachedOrbit(Rocket)
  Detached(Rocket, Capsule)
  Landed(Rocket)
}

type Notifier

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

Notifier is a notification dispatcher. It's meant to be composed, and its zero-value is ready to be used.

type Rocket struct {
  notifier notifier.Notifier
}

func RateLimited

func RateLimited(limit int) *Notifier

RateLimited returns a rate limited Notifier. only limit goroutines will be spawned. If limit is zero, no rate limiting happens. This is the same as `Notifier{}`.

func (*Notifier) Notify

func (n *Notifier) Notify(e Notifiee)

Notify signs up Notifiee e for notifications. This function is meant to be called behind your own type-safe function(s):

// generic function for pattern-following
func (r *Rocket) Notify(n Notifiee) {
  r.notifier.Notify(n)
}

// or as part of other functions
func (r *Rocket) Onboard(a Astronaut) {
  r.astronauts = append(r.austronauts, a)
  r.notifier.Notify(a)
}

func (*Notifier) NotifyAll

func (n *Notifier) NotifyAll(notify func(Notifiee))

NotifyAll messages the notifier's notifiees with a given notification. This is done by calling the given function with each notifiee. It is meant to be called with your own type-safe notification functions:

func (r *Rocket) Launch() {
  r.notifyAll(func(n Notifiee) {
    n.Launched(r)
  })
}

// make it private so only you can use it. This function is necessary
// to make sure you only up-cast in one place. You control who you added
// to be a notifiee. If Go adds generics, maybe we can get rid of this
// method but for now it is like wrapping a type-less container with
// a type safe interface.
func (r *Rocket) notifyAll(notify func(Notifiee)) {
  r.notifier.NotifyAll(func(n notifier.Notifiee) {
    notify(n.(Notifiee))
  })
}

Note well: each notification is launched in its own goroutine, so they can be processed concurrently, and so that whatever the notification does it _never_ blocks out the client. This is so that consumers _cannot_ add hooks into your object that block you accidentally.

func (*Notifier) StopNotify

func (n *Notifier) StopNotify(e Notifiee)

StopNotify stops notifying Notifiee e. This function is meant to be called behind your own type-safe function(s):

// generic function for pattern-following
func (r *Rocket) StopNotify(n Notifiee) {
  r.notifier.StopNotify(n)
}

// or as part of other functions
func (r *Rocket) Detach(c Capsule) {
  r.notifier.StopNotify(c)
  r.capsule = nil
}