Conditional compilation check for framework before importing

Question

I'm looking for a way to check if a framework exists and/or if it's classes are defined, before importing and using that framework. Specifically, the framework is Assets Library.

Currently, I'm able to do this with the Core Data framework, since that framework has a file called CoreDataDefines.h which provides a preprocessor directive _COREDATADEFINES_H. This allows me to simply check for that defintion like so:

#ifdef _COREDATADEFINES_H
#import <CoreData/CoreData.h>

// do something with Core Data

#else

// do something without using Core Data

#endif

Unfortunately, the Assets Library does not provide a clear definitions header file so I'm looking for a way to write my own #define statement that can check for the framework's existence before importing it, much like I have done for Core Data above.

I have tried this:

#if __IPHONE_OS_VERSION_MAX_ALLOWED >= 40000
// import assets library if defined !
#define ASSETSLIBRARY_DEFINE    (NSClassFromString(@"ALAsset") != nil)
#if ASSETSLIBRARY_DEFINE
#import <AssetsLibrary/AssetsLibrary.h>
#endif
#endif

... but no luck.
The compiler tells me that the "Token is not a valid binary operator in a preprocessor subexpression."

Any help is always much appreciated.

Answer 1

If you know what class should be imported with the framework you can check if it is loaded:

BOOL isFrameworkLoaded = (NSClassFromString(@"MyClassNameFromTheFramework") != nil);