[Solved] Help needed with Arduino Library

I have turned my attention to Arduino Libraries and how to create them, but I am stuck.

The following works but it is not quite what I want, here is the very simple code.

LED_KEY.h

#ifndef LED_KEY_H
#define LED_KEY_H

#include "Arduino.h"

class Led_Key  {
  public:
    // Constructor
    Led_Key(int a);    

    // Methods
    void ledON();
    void ledOFF();    

    int _a;
};
#endif

# include "LED_KEY.h"

Led_Key::Led_Key(int a){
  _a = a;
}

void Led_Key::ledON(){
  Serial.print(_a);
  Serial.println(" LED is on");
}

void Led_Key::ledOFF(){
  Serial.print(_a);
  Serial.println(" LED is off");
}

Arduino Code

#include <LED_KEY.h>

Led_Key keyLed(4);

void setup() {
  Serial.begin(9600);
  pinMode(strb, OUTPUT);
  pinMode(clk, OUTPUT);
  pinMode(data, OUTPUT);
}

void loop() {
  delay(2000);
  keyLed.ledON();
  delay(2000);
  keyLed.ledOFF();
}

What I want to do is not have "4" constantly being sent to the ledON and ledOff functions but to send a variable example ledOFF(4).

Passing a variable to a library function instead of the class.

I hope someone has got some idea of what I am talking about, Please!