@objc protocol crashes the swift compiler

问题

I wrote I protocol which was intended to have some @optional methods, but the swift compiler crashes. This works:

protocol SessionDelegate {

    // TODO these should all be optional
    func willOpenSession(session: Session);
    func didOpenSession(session: Session);
    func didFailOpenningSession(session: Session, error: NSError!);

    func willCloseSession(session: Session);
    func didCloseSession(session: Session);
}

This doesn't:

@objc protocol SessionDelegate {

    @optional func willOpenSession(session: Session);
    @optional func didOpenSession(session: Session);
    @optional func didFailOpenningSession(session: Session, error: NSError!);

    @optional func willCloseSession(session: Session);
    @optional func didCloseSession(session: Session);
}

Honestly, having @objc is enough to crash the compiler. Is there any workaround?

回答1:

Right now your only way around this is to declare the protocol in an Objective-C header file and import the declaration via an Objective-C bridging header.

Protocol declaration:

// SessionDelegate.h

@class Session;

@protocol SessionDelegate <NSObject>

@optional

- (void)willOpenSession:(Session *)session;
- (void)didOpenSession:(Session *)session;
- (void)didFailOpenningSession:(Session *)session error:(NSError *)error;

- (void)willCloseSession:(Session *)session;
- (void)didCloseSession:(Session *)session;

@end

Bridging header:

// MyProject-Bridging-Header.h

#import "SessionDelegate.h"

Conforming class implementation in Swift:

// Session.swift

class Session {
    // ...
}

class MySessionDelegate: NSObject, SessionDelegate {
    func willOpenSession(session: Session) {
        // ...
    }
}

回答2:

Apology, scratch my previous edit, try following instead:

@objc(PSessionDelegate)
protocol PSessionDelegate {

    @optional func willOpenSession(session: Session);
    @optional func didOpenSession(session: Session);
    @optional func didFailOpenningSession(session: Session, error: NSError!);
    @optional func willCloseSession(session: Session);
    @optional func didCloseSession(session: Session);

}

class ViewController: UIViewController, PSessionDelegate {

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.

    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
}

来源：https://stackoverflow.com/questions/24564830/objc-protocol-crashes-the-swift-compiler