Strongly typed NSCopying/NSMutableCopying for Swift

MutableCloning.swift

// Strongly typed NSCopying/NSMutableCopying for Swift

import Cocoa

protocol Clonable: NSCopying {
    func clone() -> Self
}

extension Clonable {
    func clone() -> Self {
        return copy(with: nil) as! Self
    }
}

protocol MutableCloning: NSMutableCopying {
    associatedtype MutableSelf
    func mutableClone() -> MutableSelf
}

extension MutableCloning {
    func mutableClone() -> MutableSelf {
        return mutableCopy(with: nil) as! MutableSelf
    }
}

extension NSParagraphStyle: MutableCloning {
    typealias MutableSelf = NSMutableParagraphStyle
}

let paragraphStyle = NSParagraphStyle.default.mutableClone()
paragraphStyle.lineBreakMode = .byTruncatingTail
print(paragraphStyle)