#include<vector> no such file or directory

Is your .h file being included in any OTHER .h or .m files?

If so, you'll have to make those (or files including them, etc) into .mm as well.

Without changing any .m to .mm or anything like that, if you click your project, click tagets->build settings go all the way down to "LLVM GCC 4.2 - Languages" you will see Compile Sources As change that value to Objective-C++;