LED library implementation see https://www.apress.com/br/book/9781430238829

LED.cpp

// LED.cpp - Example library to manipulate LEDs - public domain
#include "LED.h"

// the constructor
LED::LED(byte pin) {
	_pin = pin;               // save the pin number
	pinMode(pin, OUTPUT);     // configure pin as output
}

// the public methods
void LED::on() {
	digitalWrite(_pin, HIGH); // turn on LED
	_state = HIGH;
}

void LED::off() {
	digitalWrite(_pin, LOW);  // turn off LED
	_state = LOW;
}

void LED::toggle() {
	if(_state) {
			off();
		} else {
			on();
		}
}
	
byte LED::state() {
	return _state;
}