observer_null.go

package observer

import (
	"context"
	"fmt"
)

// ----------------------------------------------------------------------------
// Types
// ----------------------------------------------------------------------------

// NullObserver is a simple example of the Subject interface.
// It is mainly used for testing.
type NullObserver struct {
	ID       string
	IsSilent bool
}

// ----------------------------------------------------------------------------
// Interface methods
// ----------------------------------------------------------------------------

/*
The GetObserverID method returns the unique identifier of the observer.
Use by the subject to manage the list of Observers.

Input
  - ctx: A context to control lifecycle.
*/
func (observer *NullObserver) GetObserverID(ctx context.Context) string {
	_ = ctx

	return observer.ID
}

/*
The UpdateObserver method processes the message sent by the Subject.
The subject invokes UpdateObserver as a goroutine.

Input
  - ctx: A context to control lifecycle.
  - message: The string to propagate to all registered Observers.
*/
func (observer *NullObserver) UpdateObserver(ctx context.Context, message string) {
	_ = ctx

	if !observer.IsSilent {
		outputf("Observer: %s;  Message: %s\n", observer.ID, message)
	}
}

// ----------------------------------------------------------------------------
// Private functions
// ----------------------------------------------------------------------------

func outputf(format string, message ...any) {
	fmt.Printf(format, message...) //nolint
}