How to pass a Swift struct as a parameter to an Objective-C method

Question

I have an Objective-C method that accepts a parameter of type id and I want to pass it a Swift struct.

ObjcClass.m file:

@implementation ObjcClass
+ (void)addListener:(id)listener {
    // Do something with listener
}

DemoStruct.swift file:

struct DemoStruct {
    func registerAsListener() {
        ObjcClass.addListener(self) // Can't find a way to do this
    }
}

The compile error message I get:

Type 'DemoStruct' does not conform to protocol 'AnyObject'

So my question would be, how do I make an Objective-C method accept Any instead of AnyObject and is there such a thing?

Answer 1

The best thing i found was to wrap in a Box class

public class Box<T> {
    let unbox: T
    init(_ value: T) {
        self.unbox = value
    } }

Answer 2

You can't do it.

Swift structs are not accessible from Objective-C. This is stated in the "Using Swift With Cocoa and Objective-C" book from Apple:

You’ll have access to anything within a class or protocol that’s marked with the @objc attribute as long as it’s compatible with Objective-C. This excludes Swift-only features such as those listed here:

• Generics
• Tuples
• Enumerations defined in Swift
• Structures defined in Swift
• Top-level functions defined in Swift
• Global variables defined in Swift
• Typealiases defined in Swift
• Swift-style variadics
• Nested types
• Curried functions

Excerpt From: Apple Inc. “Using Swift with Cocoa and Objective-C.” iBooks. https://itun.es/gb/1u3-0.l