That is simple! There's no any difficulty but I already spent 1 day to solve it.
Answer is using Object's pointer!
To use pointer in c code, declare variable(id delegate;) top of m file.
and set a pointer to the variable as "delegate = self;"
After that, call objective c method in c code.
"[delegate callMethod];"
It works!
How come! I feel numb. y.y