For people who have been into development using Java, it should be little hard to learn Objective-C. But Apple has done a nice job allowing programmers to write Standard Cpp within their obj-c. Here is the list of things you have to ensure to avoid compilation problem.
1) Change all .m files to .mm which means you are writing Obj-c++ classes.
2) Write all your classes in cpp and .h as usually
3) You can now happily use your cpp classes in your .mm files.