It likes callback...
http://allenchou.net/2012/04/easy-c-delegates/
https://stackoverflow.com/questions/9568150/what-is-a-c-delegate
Before used delegate, you must need know function pointer.
1. https://kheresy.wordpress.com/2010/11/03/function_pointer/
2. https://kheresy.wordpress.com/2010/11/09/function_object/
3. https://kheresy.wordpress.com/2010/11/12/function_object_tr1/
Open Source:
http://marcmo.github.io/delegates/