{{define "exchanges alert" -}}
{{template "header" .}}
## Alert

+ This package allows for multiple routines to wait for a state change on any required data.

### Examples:

+ Implementation:

```go
// SomeChangingType defines an example struct with an embedded alert.Notice
// type for easy access to the notice methods.
type SomeChangingType struct {
	ValueThatChanges int64
	alert.Notice
	mu sync.Mutex // Protection for routine shenanigans
}

// Update will update in a separate routine
func (s *SomeChangingType) Update(newValue int64) {
	// This simulates a changing variable or state
	s.mu.Lock()
	s.ValueThatChanges = newValue
	// This will alert any routines that are currently waiting for a change
	s.Alert()
	s.mu.Unlock()
}

// WhatsTheValue will retrieve the value that was changed and should be
// different from the past value. Efficiency++
func (s *SomeChangingType) WhatsTheValue() int64 {
	s.mu.Lock()
	value := s.ValueThatChanges
	s.mu.Unlock()
	return value
}
```

+ Routine waiting for change:

```go
// ExampleRoutineThatWaits defines an exchange potential routine that will wait
// for an impending change.
func ExampleRoutineThatWaits(potentialChange *SomeChangingType) {
	// Every iteration requires a Wait() call.
	for range potentialChange.Wait(nil) {
		val := potentialChange.WhatsTheValue()
		fmt.Println("Value:", val)
	}
}

// AnotherExampleRoutineThatWaits defines an exchange potential routine that 
// will wait for an impending change.
func AnotherExampleRoutineThatWaits(potentialChange *SomeChangingType) {
	// Every iteration requires a Wait() call.
	for {
		select {
			case <-potentialChange.Wait(nil):
				val := potentialChange.WhatsTheValue()
				fmt.Println("Value:", val)
			case <-shutdownChannel:
				fmt.Println("Good-Bye!")
			return 
		}
	}
}


// WARNING: PLEASE DON'T DO THIS.
// This will stop alerting for this specific data type due to the shared nature 
// of the underlying channels using a sync.Pool.
func ABadExampleRoutineThatWaits(potentialChange *SomeChangingType) {
	capturedChannel := potentialChange.Wait(nil)
	for {
		select {
			case <-capturedChannel:
				// This will produce incorrect results or no change. 
				val := potentialChange.WhatsTheValue()
				fmt.Println("Value:", val)
			case <-shutdownChannel:
				fmt.Println("Good-Bye!")
			return 
		}
	}
}
```

### Please click GoDocs chevron above to view current GoDoc information for this package
{{template "contributions"}}
{{template "donations" .}}
{{end}}