mixing objective-c and swift when subclassing

56
votes

I've got a subclass of UIViewController written in Swift called 'BaseViewController'. I now have an 'old' view controller called 'ViewController1' written in Objective-C that I want to inherit from 'BaseViewController'. Following other advice I have imported the 'Project-Swift.h' header file.

My problem occurs when subclassing like this

#import <UIKit/UIKit.h>
#import "MyProject-Swift.h"

@interface ViewController1 : BaseViewController
@end

The error is:

Cannot subclass a class with objc_subclassing-restricted attribute

and it appears on the @interface ... line.

3
iosobjective-cswift
Writing a new superclass to an existing class seems a little odd to me... - nhgrif
I think OP's question is just about how to have an Objective-C class extend a Swift class, which is not possible - Craig Otis

3 Answers

10
votes

You cannot subclass a Swift class in Objective-C. cf. towards the end of this section of the docs:

However, note that you cannot subclass a Swift class in Objective-C.

0
votes

It's an compiling error, so U can not subclass a swift class in objc. 

SWIFT_CLASS("_TtC6Swifty14ViewController")
@interface ViewController : UIViewController
@end


# if defined(__has_attribute) && __has_attribute(objc_subclassing_restricted)
#  define SWIFT_CLASS(SWIFT_NAME) SWIFT_RUNTIME_NAME(SWIFT_NAME) __attribute__((objc_subclassing_restricted)) SWIFT_CLASS_EXTRA
#  define SWIFT_CLASS_NAMED(SWIFT_NAME) __attribute__((objc_subclassing_restricted)) SWIFT_COMPILE_NAME(SWIFT_NAME) SWIFT_CLASS_EXTRA
# else
#  define SWIFT_CLASS(SWIFT_NAME) SWIFT_RUNTIME_NAME(SWIFT_NAME) SWIFT_CLASS_EXTRA
#  define SWIFT_CLASS_NAMED(SWIFT_NAME) SWIFT_COMPILE_NAME(SWIFT_NAME) SWIFT_CLASS_EXTRA
# endif
#endif