RelayResponder.swift

//
//  Relay.swift
//  XjSwiftLab
//
//  Created by Jason Jobe on 5/11/15.
//  Copyright (c) 2015, 2016 Jason Jobe. All rights reserved.
//  https://gist.github.com/wildthink/acfdf82c2625dc73ad6e42d399d91846
//

/* Example usage
    protocol SomeClassOrProtocol.self) {
        func someClassOrProtocolFunction (some:Int, args:[String])
    }
    relay (SomeClassOrProtocol.self) {
       $0.someClassOrProtocolFunction(some, args)
    }
    relay { (target: SomeClassOrProtocol) in
        target.someClassOrProtocolFunction(some, args)
    }

    protocol Demo {}
    let app = Application.shared

    let demo = app.relay(type: Demo.self)
    let demo2: Demo? = app.relay()
*/

import Foundation

#if os(iOS)
    import UIKit.UIResponder
    public typealias Responder = UIResponder
    public typealias Application = UIApplication
#else
    import AppKit.NSResponder
    public typealias Responder = NSResponder
    public typealias Application = NSApplication
#endif

public extension NSObjectProtocol where Self: Responder
{
    func relay <T> (type: T.Type, call: (T) -> Void) -> Void {
        if let target = relay(type: type) { call (target) }
    }

    func relay <T> (type: T.Type, if test: (T) -> Bool, call: (T) -> Void) -> Void {
        if let target = relay(type: type) { call (target) }
    }

    func relay<T>() -> T? {
        if let target = relay(type: T.self) { return target }
        return nil
    }

    func relay <T> (type: T.Type, if test: ((T) -> Bool)? = nil) -> T?
    {
        var next: Responder? = self

        while next != nil {
            if let t = next as? T, test?(t) ?? true {
                return t
            }
            next = next?.next
        }
        if let t = Application.shared.delegate as? T, test?(t) ?? true {
            return t
        }
        return nil
    }
}