Return value from custom class

Using Arduino Programming Questions
1

Hi,

After many hours, I can't figure out how this works. a void works just fine, but the second I use int all hell breaks loose.

I have tried everything but for some reason I keep getting either

argument type of 'int (Instrumentation::)()'does not match 'int'

or

expected constructor, destructor, or type conversion before 'Instrumentation'

Please help, I'm sure you can return something from a class I just cant find/figure out how.

Here is my attempt:

Instrumentation.h file

/*
  Instrumentation.h
*/
#ifndef Instrumentation_h
#define Instrumentation_h
  
  #include "WProgram.h"

  class Instrumentation
  {
    public:
      Instrumentation();
      ~Instrumentation();
       int BatteryVoltage();  
    private:
      int Test;
  }; 
#endif

Instrumentation.cpp file

/*
  Instrumentation.cpp
*/
#include "WProgram.h"
#include "Instrumentation.h"
// Constructor
Instrumentation::Instrumentation()
(
  // Constructor/Initializer
)

// Destructor
Instrumentation::~Instrumentation(){/*nothing to destruct*/}
  
int Instrumentation::BatteryVoltage
{
  int intBatteryVoltage = analogRead(A1);
  // Scale ADC value Here
  return intBatteryVoltage;   
}

Test.pde

#include "Instrumentation.h"

Instrumentation instrumentation;

void setup() 
{                
  Serial.begin(9600); 
  Serial.println("Serial Util"); 
}

void loop() {
  char InputChr;
  // check if data has been sent from the computer:
  //if (Serial.available()) {
  //  // read the most recent byte (which will be from 0 to 255):
  //  InputChr = Serial.read();
  int Test = instrumentation.BatteryVoltage;
  Serial.println(Test);
  delay(3000);
  
  }

BTW is it posible to have the code in the h file and cpp file in a single file?

Thanks

2 
int Instrumentation::BatteryVoltage
{
  int intBatteryVoltage = analogRead(A1);
  // Scale ADC value Here
  return intBatteryVoltage;   
}

This won't compile unless you put parenthesis at the end of the first line. It's a function after all.
Also use parenthesis when you call the function:

int Test = instrumentation.BatteryVoltage();