after reading and doing several testing i found out answers in my questions...

how to export class functions...

mydll.h
Qt Code: 
  1. #define MYDLLEXPORT Q_DECL_EXPORT
  2. #ifndef MYDLL_H
  3. #define MYDLL_H
  4.  
  5. #include "ui_your_ui.h // if you have used ui in your class 
  6.  
  7.  
  8. class your_class //some codes
  9. {
  10. //some codes
  11. class_function();
  12. }
  13. extern "C" {
  14. MYDLLEXPORT void showqt();  
  15. ...
  16. ..
  17. }
  18. #endif
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your_class.cpp
Qt Code: 
  1. #include mydll.h
  2. class::class
  3. {
  4. //some lines.........
  5. }
  6. class::class_fuction()
  7. {
  8. //some lines..........
  9. }
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mydll.cpp
Qt Code: 
  1. #include <QApplication>
  2. #include "mydll.h"
  3.  
  4. int main()
  5. {
  6.  
  7. }
  8.  
  9. void showqt()
  10. {
  11. char ** argv;
  12. int argc=1;
  13.  
  14. QApplication lib(argc,argv);
  15. your_class accessclass;//this should be under the QApplication or paint event
  16.  
  17. acessclass.class_function(); //to access the class functions
  18.  
  19. return;
  20. }
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the point here is to access the class::function to exported function


and lastly to access the functions with parameter depends on how you imported the function....

if you have suggestions on how can i improve my program, you are free to comment..