Threading an instance of a class which has no dependency upon Qt

[menasce]

I need to be able to launch a sub-classed QThread in such a way that the run() protected method of QThread calls different objects depending upon a class-member variable. Let's see an example.

This is the header of my sub-classed QThread:

#ifndef THREADLAUNCHER_H
#define THREADLAUNCHER_H
 
#include <QThread>
#include "someProcess.h"
 
class threadLauncher : public QThread
{
    Q_OBJECT
public:
    void run() ;
    void setClass(someProcess * aProcess) ;
private:
    someProcess * theProccess_ ;
};
 
#endif

#ifndef THREADLAUNCHER_H
#define THREADLAUNCHER_H

#include <QThread>
#include "someProcess.h"

class threadLauncher : public QThread
{
    Q_OBJECT
public:
    void run() ;
    void setClass(someProcess * aProcess) ;
private:
    someProcess * theProccess_ ;
};

#endif

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Now the source-code of the implementation:

#include "someProcess.h"
#include "threadLauncher.h"
 
void threadLauncher::run()
{
  theProccess_->compute() ;
}
 
void threadLauncher::setClass(someProcess * aProcess)
{
  theProccess_ = aProcess ;
}

#include "someProcess.h"
#include "threadLauncher.h"

void threadLauncher::run()
{
  theProccess_->compute() ;
}

void threadLauncher::setClass(someProcess * aProcess)
{
  theProccess_ = aProcess ;
}

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In the main program this is the way I launch the thread:

int main()
{
  QApllication app() ;
 
  someProcess * theProcessA_ = new someProcess() ;
 
  threadLauncher * theThreadLauncher_ = new threadLauncher() ;
  theThreadLauncher_->setClass(theProcessA_) ;
  theThreadLauncher_->start() ;
 
  app.exec() ;
}

int main()
{
  QApllication app() ;
  
  someProcess * theProcessA_ = new someProcess() ;

  threadLauncher * theThreadLauncher_ = new threadLauncher() ;
  theThreadLauncher_->setClass(theProcessA_) ;
  theThreadLauncher_->start() ;

  app.exec() ;
}

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This is working fine: now comes the tricky part (and my question).
I would like to execute different things in the re-implemented 'run' method. One (trivial) possibility could be:

int main()
{
  QApllication app() ;
 
  someProcess      * theProcessA_ = new someProcess() ;
  classBDefinition * theProcessB_ = new classBDefinition() ;
 
  threadLauncher * theThreadLauncher_ = new threadLauncher() ;
  theThreadLauncher_->setClass(theProcessA_) ;
  theThreadLauncher_->start() ;
 
  theThreadLauncher_->setClass(theProcessB_) ;
  theThreadLauncher_->start() ;
 
  app.exec() ;
}

int main()
{
  QApllication app() ;
  
  someProcess      * theProcessA_ = new someProcess() ;
  classBDefinition * theProcessB_ = new classBDefinition() ;

  threadLauncher * theThreadLauncher_ = new threadLauncher() ;
  theThreadLauncher_->setClass(theProcessA_) ;
  theThreadLauncher_->start() ;
  
  theThreadLauncher_->setClass(theProcessB_) ;
  theThreadLauncher_->start() ;
  
  app.exec() ;
}

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This would allow me to launch two completely different computations (implemented in different classes) using a single instance of a threadLauncher. My problem at this point is how to make the mechanism general (template?). Infact, to be able to run the latter example I should modify the threadLauncher to become the following:

#ifndef THREADLAUNCHER_H
#define THREADLAUNCHER_H
 
#include <QThread>
#include "someProcess.h"
#include "classBDefinition.h"
 
class threadLauncher : public QThread
{
    Q_OBJECT
public:
    void run() ;
    void setClass(someProcess      * aProcess) ;
    void setClass(classBDefinition * aProcessB) ;
private:
    someProcess      * theProccessA_ ;
    classBDefinition * theProccessB_ ;
};
 
#endif

#ifndef THREADLAUNCHER_H
#define THREADLAUNCHER_H

#include <QThread>
#include "someProcess.h"
#include "classBDefinition.h"

class threadLauncher : public QThread
{
    Q_OBJECT
public:
    void run() ;
    void setClass(someProcess      * aProcess) ;
    void setClass(classBDefinition * aProcessB) ;
private:
    someProcess      * theProccessA_ ;
    classBDefinition * theProccessB_ ;
};

#endif

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and the source, accordingly:

#include "someProcess.h"
#include "threadLauncher.h"
 
void threadLauncher::run()
{
  if( theProccessA_ ) theProccessA_->compute() ;
  if( theProccessB_ ) theProccessB_->compute() ;
}
 
void threadLauncher::setClass(someProcess * aProcess)
{
  theProccessA_ = aProcess ; 
}
 
void threadLauncher::setClass(classBDefinition * aProcess)
{
  theProccessB_ = aProcess ;  
}

#include "someProcess.h"
#include "threadLauncher.h"

void threadLauncher::run()
{
  if( theProccessA_ ) theProccessA_->compute() ;
  if( theProccessB_ ) theProccessB_->compute() ;
}

void threadLauncher::setClass(someProcess * aProcess)
{
  theProccessA_ = aProcess ; 
}

void threadLauncher::setClass(classBDefinition * aProcess)
{
  theProccessB_ = aProcess ;  
}

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This is obviously not manageable should the possibilities increase. My first though was to make the threadLauncher a template class, but since it inherits from a QThread I cannot (I was thinking something like this would do:

#ifndef THREADLAUNCHER_H
#define THREADLAUNCHER_H
 
#include <QThread>
 
template <class T> threadLauncher : public QThread
{
    Q_OBJECT
public:
    void run() ;
    void setClass(T * aProcess) ;
private:
    T * theProccessA_ ;
};
 
#endif

#ifndef THREADLAUNCHER_H
#define THREADLAUNCHER_H

#include <QThread>

template <class T> threadLauncher : public QThread
{
    Q_OBJECT
public:
    void run() ;
    void setClass(T * aProcess) ;
private:
    T * theProccessA_ ;
};

#endif

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I know this is absolutely incorrect C++, I meant it just to convey the basic idea.

Is there some useful suggestion I could receive?

Thanks

[high_flyer]

Before getting in to details - have you checked QtConcurrent?
It looks to me, your case exactly meant for that.
It will save you the whole sub classing issue.