NSDictionary-C ++中的Objective-C代码

Question

Is it possible to use NSDictionary inside C++ class ? I know, I can use Objective-C classes inside C++ ( http://philjordan.eu/article/mixing-objective-c-c++-and-objective-c++ ), but for NSDictionary , I need header... but if I do #import , it failed to compile.

PS: I know, I shouldnt mix Objective-C(++) and C++ , but I am writing multiplatform OpenGL app and for EAGL initialization one of input parametrs is NSDictionary . I could init OpenGL in Objective-C , but it would break my OOP design.

Answer 1

Sure compile the C++ class as Objective-C++ (.mm extension) and you will have no problems. The only problem I've had doing this is the fact that you can't define the Objective-C++ type inside the C++ header. So instead I use a void* and cast it to void* using a

pVoidDict = (__bridge_retained void*)[NSDictionary dictionary];

You will need to perform a bridged cast to use it:

unsigned int dictCount = [(__bridge NSDictionary*)pVoidDict count];

The only problem is you must remember to release it at the end. You can do this by casting it back to an NSDictionary as follows:

NSDictionary* dict = (__bridge_transfer NSDictionary*)pVoidDict;

This will return it to ARC control and when the destructor exits it will be added to the autorelease pool as per standard ARC rules.

Its not particularly nice to look at but I use this quite a bit in a cross-platform library so that I can wrap Objective-C objects with C++ classes.