Passing an Objective-C protocol to an objective-C function in Swift?

[JetForMe (Rick M)]

I'm trying to convert an old Obj-C project to Swift. I'm using an esoteric serialization protocol called Hessian that gets configured with calls like this:

[CWHessianUnarchiver setProtocol: @protocol(MissionProtocol) forClassName: @"com.some.java.server.class.ClientV1Mission"];

…

@protocol MissionProtocol
// Properties…
@end

In Swift, the calls look like this, but this isn’t quite right, and I'm not sure how to write it:

CWHessianUnarchiver.setProtocol(MissionProtocol.Type, forClassName: "com.some.java.server.class.ClientV1Mission")

But I get {Cannot convert value of type '(any MissionProtocol.Type).Type' to expected argument type 'Protocol?'" for the setProtocol call. How should I pass this?

[bbrk24]

Objective-C Protocol objects, like Swift metatypes, are spelled P.self, not P.Type.

[Kyle-Ye (Kyle)]

The 2 posts may help solve your problem.

Swift metatype and ObjectiveC Protocol question

We have an ObjC API which receive a Protocol instance and return Any?. // Imported ObjectiveC API func resolve(_ p: Protocol) -> Any? // Swift Side Code @objc protocol P: NSObjectProtocol { func hello() } func test() { let p = resolve(P.self) as? P p?.hello() } In Swift side, we'd like to wrap the API to make it more swift-friendly. func resolve2<T>(_ t: T.Type) -> T? { return resolve(t) as? T // return resolve(t.self) as? T // return resolve(T.self) as? T // …

What's .self, .Type and .Protocol? Understanding Swift Metatypes

[JetForMe (Rick M)]

@bbrk24

Objective-C Protocol objects, like Swift metatypes, are spelled P.self, not P.Type.

I tried that, but it didn't work. However, I just tried it again, and it works. I must've not tried. But now I'm questioning my sanity. Thanks!