[Xcode] Fixed: Build error that it import Objective-C codes in the .cpp?

Build error: (NSObjCRuntime.h & NSObject)

/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObjCRuntime.h:371:1: Expected unqualified-id

/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObjCRuntime.h:373:19: Unknown type name 'NSString'
...

/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/include/objc/NSObject.h:11:1: Expected unqualified-id
...


[Solution]
rename extension name from .cpp into .mm