@objc protocol crashes the swift compiler

Question

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?

Answer 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) {
        // ...
    }
}