Calling C++ classes and methods within Objective-C

Question

I'm working on an iOS application where most of the backend has already been done in C++. The interface is obviously in Obj-C and I'm not sure how to use the two languages at the same time together.

Basically, I want to have a Song datamember in my Objective-C file and than perform these kind of actions to that song datamember/object:

Song song("Hardcore Beatzzz", "RockzStarsz", 60);
song.setTimeSig(4,4);

Track synthTrack;
synthTrack.setTrackName("sinussynth #1");

Note note3(880, 100, 8, 1, 17);
synthTrack.addNote(note3);

playlist.addTrack(synthTrack);

So obviously this is all C++ but how would I do this within my Objective-C files?

Answer 1

Make a file with .mm extension and the compiler will treat it is an Objective-C++ source code. This would allow you to mix the C++ and Objective-C code.

Basically, you can call C++ functions and declare the variables which have the C++ class type.

In the .mm file you should include the .h files for your C++ code and then use the C++'s declarations in Objective-C.

One sufficient restriction: you cannot inherit C++ classes from Objective-C interfaces and vice versa.

Of course, the "best" part is the need for manual memory management for C++ objects (see rickster's comment). There is not automatic garbage collection, so when you declare pointers and allocate some memory you've got to deallocate them later.