Setter.h

// Setter.h
//
// Virtual base class for classes that receive a value, maybe transform it and do something with it
// 
/// \author  Mike McCauley (mikem@airspayce.com)
///
// Copyright (C) 2010 Mike McCauley
// $Id: Setter.h,v 1.4 2018/09/17 23:09:57 mikem Exp mikem $
 
#ifndef Setter_h
#define Setter_h
 
/////////////////////////////////////////////////////////////////////
/// \class Setter Setter.h <Setter.h>
/// \brief Virtual base class for classes that receive a value, maybe transform it and then 
/// do something with it
///
/// Setters (ie different subclasses of Setter) are designed to be chained together.
/// Each Setter in a chain transforms its input value in some way and then maybe passes it on to 
/// its output Setter.
/// Setters can be designed to do almost any transformation with a number, including 
/// changing it, sending it to some device, using the value to set a physical output etc.
/// Each setter can accept as input an int (ie a 16 bit signed number) although some Setters
/// may be more constrained as to which value ranges make physical sense.
class Setter
{   
public:
    /// Constructor.
    Setter();
 
    /// Constructor with setting the target 
    Setter(Setter* target);
 
    /// This is where incoming values are set.
    // This default implementation merely passes its value to the output
    /// \param[in] value The input value
    virtual void input(int value);
 
    /// Connects this Setter to a downstream Setter
    /// \param[in] target Pointer to a sublass of Setter, whose input() function will be called
    /// when a new value is available from this Setter.
    virtual void setTarget(Setter* target);
 
    /// Called when the source of input data is lost, and the Setter is required to fail in a safe way.
    /// Subclasses can override.
    /// Default is to send to next Setter in the chain.
    virtual void failsafe();
 
    /// Sets the failsafeValue
    void setFailsafeValue(int failsafeValue);
 
    /// Returns the most recently set failsafe value.
    /// Base class does not use this
    int failsafeValue();
 
    
protected:
    /// This is the instance of Setter that will be given the transfotmed output value
    Setter* _target;
 
    /// This is the failsafe value, which some setters use to set the output when
    /// a failsafe call is made
    int     _failsafeValue;
 
private:
};
 
#endif