从Objective C中的Swift类继承

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.

我在Xcode 7项目中成功地混合和匹配Obj-C和Swift。但是，我似乎无法弄清楚在Objective C类中如何从Swift类继承（是的，我知道将Swift类声明为@objc以获得可见性）。在这种情况下，所需的Swift超类MySwiftViewController是UIViewController的子类。现在，在Obj-C中，我直接从UIViewController继承并且无法访问我在MySwiftViewController中添加的功能。

Here's what i understand:

这是我的理解：

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

- 要将Obj-C类声明为继承某些东西，它必须位于'：'之后的.h文件中：

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

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

- 要使Swift类可见，那就是#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?

但是，您无法将Swift自动生成的桥接头导入Obj-C .h文件。您也无法使用@class正向声明不透明的超类。那么，这可能吗？如何？

2 个解决方案

#1

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

不幸的是，不可能在Objective-C中继承Swift类。直接来自文档：

You cannot subclass a Swift class in Objective-C.

您不能在Objective-C中继承Swift类。

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

有关使用Objective-C可以访问和不能访问的内容的更多详细信息，请参阅Apple的互操作性指南。

#2

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

对于Xcode 8.0和更早版本，有一个肮脏的hacky解决方案，可能将来会修复。

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

如果要从swift文件中继承子类，可以添加objc_subclassing_restricted属性。为方便起见，您可以将其设为宏。码：

Swift class.

斯威夫特班。

import Foundation

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

Objc class:

Objc类：

#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.

但是，据我所知，它不受支持，因此你可能会遇到任何类型的错误。所以它不是行动的指南，更像是好奇的事情要知道。

#1