Instance of DHT class within specialised class

Paul,

As I say the main sketch does nothing with my class yet as it doesn't compile, but here it is;

/*
  LMS10000 EECS -  LMS 10000 Engine Electronic Contol System
  Copyright (c) 2012 Mark Batchelour.  All right reserved.
*/


// Includes ------------------------------------------------------------------------------------------------------
#include "LMS10000Constants.h"
#include <SerialCommand.h>
#include <LCD5110.h>
#include "DHT22TempHumidity.h"

// Locals ------------------------------------------------------------------------------------------------------
SerialCommand SCmd;   // The demo SerialCommand object

boolean SerialOutputEnabled = true;
boolean UseAuthorised = false;
String  StatusMessage = "";
String  ParamMessage = "";





// Setup ------------------------------------------------------------------------------------------------------
void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600); 

  LcdInitialise();
  LcdClear();
 
  gotoXY(LCDLeft,LCDBannerLine);
  LcdString(LCDbannerString);
  
  // Setup callbacks for SerialCommand commands 
  SCmd.addCommand(ControlPassword,PasswordGiven);       // Turn on serial output
  SCmd.addCommand(EngineStopCmdshort,StopEngine);           // Turns engine off
  SCmd.addCommand(EngineStopCmd,StopEngine);        // Turns engine off
  SCmd.addCommand(MonitorOffCmd,MonitoringOff);        // Turns monitoring off
  SCmd.addCommand(MonitorOnCmd,MonitoringOn);        // Turns monitoring off
  SCmd.addDefaultHandler(unrecognized);  // Handler for command that isn't matched  (says "What?") 
  Serial.println(RemoteReadyPrompt); 
}


// Security Functions ------------------------------------------------------------------------------------------
void PasswordGiven()
{
   UseAuthorised = true;
   Serial.println(RemoteAuthorisedMsg); 
   Serial.println(RemoteReadyPrompt); 
   StatusMessage += RemoteMonEnableMsg;
}




void unrecognized()
{
   Serial.println(RemoteBadCmdMsg); 
   Serial.println(RemoteReadyPrompt); 
}


void MonitoringOn()
{
  if (UseAuthorised)
  {
      SerialOutputEnabled = true;
      StatusMessage = RemoteMonEnableMsg;
      Serial.println(RemoteMonEnableMsg); 
      Serial.println(RemoteReadyPrompt); 
  }
  else
  {
      Serial.println(RemoteNotAuthMsg);
      Serial.println(RemoteReadyPrompt); 
  }
}



void MonitoringOff()
{
  if (UseAuthorised)
  {
      SerialOutputEnabled = false;
      StatusMessage += RemoteMonDisableMsg;
      Serial.println(RemoteMonDisableMsg); 
      Serial.println(RemoteReadyPrompt); 
  }
  else
  {
      Serial.println(RemoteNotAuthMsg); 
      Serial.println(RemoteReadyPrompt); 
  }
}

// Engine control ----------------------------------------------------------------------------------------------------------------
void StopEngine()
{
  if (UseAuthorised)
  {
      // stop the engine
        Serial.println(RemoteEngStopMsg); 
        StatusMessage += RemoteEngStopMsg;
        Serial.println(RemoteReadyPrompt); 
  }
  else
  {
      Serial.println(RemoteNotAuthMsg); 
      Serial.println(RemoteReadyPrompt); 
  }

}


// main ----------------------------------------------------------------------------------------------------
void loop() {
  //pause for a while
  delay(UpdateInterval);
  
  // read serial commands
  
  SCmd.readSerial(); 
  
  // read sensors
  
  // Dispay parameters
  
  // Evaluate warnings
  
  // Raise alarms
  if (SerialOutputEnabled == true)
  {
 
  }
   
  gotoXY(LCDLeft,LCDStatusLine);
  Scroll(StatusMessage);
  gotoXY(LCDLeft,LCDParamLine);
  Scroll(ParamMessage);
}

and here is the body of the DHT22TempHumidity class;

/*
  DHT22TempHumidity - basic template for LMS 10000 sensor
  Copyright (c) 2012 Mark Batchelour.  All right reserved.
  LMS 10000 reCreation project.     www.LMS10000.org
*/

// ensure this library description is only included once
#ifndef DHT22TempHumidity_h
#define DHT22TempHumidity_h

// include types & constants of Wiring core API
#include "Arduino.h"
#include <dht.h>

// library interface description
class DHT22TempHumidity
{
  // user-accessible "public" interface
  public:
    DHT22TempHumidity(int);
    float GetValue(void);
    float ReadSensor(void);
    void  DisplaySerial(void);
    void  DisplayLcd(void);
    dht   SensorDHT22;   

  // library-accessible "private" interface
  private:
    float value;
   

};

#endif