gistfile1.swift

import Foundation


struct ConversationViewSnapshot : Diffable {
    
    func diffWith(diffable: ConversationViewSnapshot) -> ConversationViewDiff {
        return ConversationViewDiff.None
    }
    
    func applyDiff(diff: ConversationViewDiff) -> ConversationViewSnapshot {
        return self
    }
}

enum ConversationViewDiff : Diff {
    typealias BaseType = ConversationViewSnapshot
    case None
    
    func mergeWithDiff(diff: ConversationViewDiff) -> ConversationViewDiff {
        return .None
    }
}

struct Conversation {
    
}

protocol Diff {
    typealias BaseType
    func mergeWithDiff(diff:Self) -> Self
}

protocol Diffable {
    func diffWith<B: Diff where B.BaseType == Self>(diffable:Self) -> B
    func applyDiff<B: Diff where B.BaseType == Self>(diff:B) -> Self
}