Inherit from a Swift class in Objective C

Question

I'm successfully mixing and matching Obj-C and Swift in an Xcode 7 project. However, I can't seem to figure out how, in an Objective C class, to inherit from a Swift class (and yes I know about declaring that Swift class as @objc for visibility). In this case the desired Swift superclass MySwiftViewController is a subclass of UIViewController. For now, in Obj-C, I'm inheriting directly from UIViewController and not gaining access to the capabilities I added in MySwiftViewController.

Here's what i understand:

-- To declare an Obj-C class as inheriting from something, that must be in the .h file after the ':':

#import <UIKit/UIKit.h> @interface RootViewController : UIViewController <UITableViewDataSource, UITableViewDelegate> @end 

-- To make Swift classes visible, that is #imported:

#import "MyProject-Swift.h" 

However, you cannot import the Swift auto-generated bridging header into the Obj-C .h file. You also cannot forward-declare an opaque superclass with @class. So, is this possible and how?

Answer 1

Unfortunately, it's not possible to subclass a Swift class in Objective-C. Straight from the docs:

You cannot subclass a Swift class in Objective-C.

See Apple's guide on interoperability for more details on what you can and cannot access with Objective-C.

Answer 2

As for Xcode 8.0 and earlier there is dirty-hacky solution, that probably will be fixed in the future.

If you want to subclass from swift file, you can add objc_subclassing_restricted attribute. You can make it as macro for convenience. Code:

Swift class.

import Foundation  class SwiftClass : NSObject {   func say() {     print("hi");   } } 

Objc class:

#import <Foundation/Foundation.h>  #import "test-Swift.h"  #define SWIFT_SUBCLASS __attribute__((objc_subclassing_restricted))  SWIFT_SUBCLASS @interface ObjcClass : SwiftClass - (instancetype)init; @end @implementation ObjcClass - (void)say {   NSLog(@"oops"); } @end 

But, as I understand, it is not supported, and you may have any sort of bugs because of it. So it is not guide to action, and more like curious thing to know.