A stupid forward declaration made one of my whole day miserable.
At the time it says the class cannot be found, I put the forward declaration in the front of the header file. And that, turned out, still, not working. As a result of no result from googling, I put off all that-class-related method wrapping and continued on other part of my work.
Now the reason comes to surface. Stupid ME put the stupid forward declaration outside the namespace symbol. THAT is the reason, and that is THE reason, why I wasted that much time.
Stupid me, learn, and go forward.
