void value not ignored as it ought to be

Using Arduino Programming Questions
13

here is all the updated code if it helps, main ino file:

#include <CapacitiveSensor.h> 
#include "Letter.h"

const byte capSenseSend = 2;

const byte numberOfSensors = 2;
Letter letters[numberOfSensors]; // a-z


const byte sensorPin[] = { 22, 23 };
const byte ledPin[] = { 8 };

int allValues[numberOfSensors];

void setup(){
   Serial.begin(19200);
   delay(100);
   
   CapacitiveSensor cs_sensor[numberOfSensors];
   
   for(int i = 0; i < numberOfSensors; i++){
     cs_sensor[i] = CapacitiveSensor(capSenseSend,sensorPin[i]);
   }
  
   // setup LEDs
   for(int i = 0; i < numberOfSensors; i++){
     pinMode(ledPin[i],OUTPUT);
     digitalWrite(ledPin[i], LOW);  
   }
   //cs_a.set_CS_AutocaL_Millis(0xFFFFFFFF); 

   setSampleSize();   
}

void loop(){  
    setSensorValue();
    checkIfButtonPressed();
    delay(100);
}

void setSampleSize(){
  for(int i = 0; i < numberOfSensors; i++){ 
    letters[i].setSampleAmount(5);
  }
}

void setSensorValue(){
  for(int i = 0; i < numberOfSensors; i++){
    letters[i].setCurrentReading(cs_sensor[i].capacitiveSensor(50));  
  }
}

void checkIfButtonPressed(){
  for(int i = 0; i < numberOfSensors; i++){ 
    letters[i].checkIfIsOn(cs_sensor[i]); 
  }
}

void fadeLedIn(int pinNumber){ 
  for(int j = 0; j <= 255; j+=10){
    analogWrite(pinNumber,j);
    delay(10);
  }  
}

void fadeLedOut(int pinNumber){ 
  for(int j = 255; j >= 0; j-=10){
    analogWrite(pinNumber,j);
    delay(10);
  }  
  digitalWrite(pinNumber, LOW); 
}

void sendSerialData(int buttonTouched){
  delay(10); Serial.print("Data,");
  delay(10); Serial.print(buttonTouched);
  delay(10); Serial.print(",");
  Serial.print("sensors : ");
  Serial.print(allValues[0]); Serial.print(" , "); Serial.print(allValues[1]); delay(10);
  Serial.print("\n");
  delay(10);
}

Letter.h

#ifndef LETTER_H
#define LETTER_H

class Letter {
  public:
    Letter();
    double getAverage(int sample);
    void setSampleAmount(int changeSampleTo);
    void setLastReading(int theLastReading);
    void setCurrentReading(int theCurrentReading);
    void checkIfisOn(int curentSensorValue[]);
    int getCurrentReading();
    int getLastReading();
    int aValue;
    int lastReading;
    int currentReading;
  private:
    
    int _sampleAmount;
    double _tempAverage,
           _capacitiveAverage;
    double _runningAverage[100];
};

#endif

Letter.ino

#include "Letter.h" // "" for files within same folder as sketch...?

Letter::Letter() {
  _sampleAmount = 5;
  _tempAverage = 0;
  _capacitiveAverage = 0;  
  lastReading = 0;
  currentReading = 0;
  //long _runningAverage[_sampleAmount];
};

void Letter::setSampleAmount(int changeSampleTo){
  _sampleAmount = changeSampleTo;
}; 

void Letter::setLastReading(int theLastReading){
  lastReading = theLastReading;
}

void Letter::setCurrentReading(int theCurrentReading){
  currentReading = theCurrentReading;
}

int Letter::getLastReading(){
  return lastReading;
}

int Letter::getCurrentReading(){
  return currentReading;
}

double Letter::getAverage(int sample) {
  for(int i = 0; i < _sampleAmount; i++){
    _runningAverage[i] = sample;
  } 
  // reset _tempAverage
  _tempAverage = 0;
  // add all the samples up
  for(int i = 0; i < _sampleAmount; i++){
    _tempAverage += _runningAverage[i];
  } 
  // divide by number of samples to get average
  _capacitiveAverage =  _tempAverage/_sampleAmount;
  return _capacitiveAverage;
}


void Letter::checkIfisOn(){
  boolean firstTime = true;
  int firstRelease = 0;
  const int threshold = 55;
  int differenceReading = curentSensorValue-lastReading;
  if(differenceReading > threshold && firstTime == true){
    sendSerialData(i);
    fadeLedIn(ledPin[i]);
  if((currentReading-lastReading) < threshold){
    digitalWrite(ledPin[i], LOW); 
    fadeLedOut(ledPin[i]);}
    lastReading[i] = currentReading[i];
    firstTime = false;
  }
}