PureSwiftResponderChain.swift

import UIKit

// Message Type
struct Message<Target> {
    let action: (Target) -> ()
    
    init(_ action: (Target) -> ()) {
        self.action = action
    }

    func deliverAlong(chain: [Any]) {
        for object in chain {
            if let receiver = object as? Target {
                action(receiver)
            }
        }
    }
}


// Target Protocol
protocol DoesSomething {
    func doSomething()
}


// Receiver
class ReceivingObject : DoesSomething {
    func doSomething() {
        print("Message Received!")
    }
}


// Chain with receiver
let chain: [Any] = [ReceivingObject()]


// Create a message
let message = Message<DoesSomething>({ $0.doSomething() })


// Send message
message.deliverAlong(chain)