vikitripathi · January 26, 2018 21:47 · Oct 15, 2016
diff --git a/Event.swift b/Event.swift
@@ -0,0 +1,52 @@
+public struct Event {
+    public internal(set) var timeStamp: Date
+    public internal(set) var eventTag: String
+
+    public init(timeStamp: Date, tag: String) {
+        self.timeStamp = timeStamp
+        self.eventTag = tag
+    }
+}
+
+extension Event {
+    class Coding: NSObject, NSCoding {
+        let event: Event?
+
+        init(event: Event) {
+            self.event = event
+            super.init()
+        }
+
+        required init?(coder aDecoder: NSCoder) {
+            guard let timeStamp = aDecoder.decodeObject(forKey: "timeStamp") as? Date, 
+                  let eventTag = aDecoder.decodeObject(forKey: "eventTag") as? String else {
+                return nil
+            }
+
+            event = Event(timeStamp: timeStamp, tag: eventTag)
+
+            super.init()
+        }
+
+        public func encode(with aCoder: NSCoder) {
+            guard let event = event else {
+                return
+            }
+
+            aCoder.encode(event.timeStamp, forKey: "timeStamp")
+            aCoder.encode(event.eventTag, forKey: "eventTag")
+        }
+    }
+}
+
+extension Event: Encodable {
+    var encoded: Decodable? {
+        return Event.Coding(event: self)
+    }
+}
+
+extension Event.Coding: Decodable {
+    var decoded: Encodable? {
+        return self.event
+    }
+}
diff --git a/Protocols.swift b/Protocols.swift
@@ -0,0 +1,21 @@
+protocol Encodable {
+    var encoded: Decodable? { get }
+}
+
+protocol Decodable {
+    var decoded: Encodable? { get }
+}
+
+
+extension Sequence where Iterator.Element: Encodable {
+    var encoded: [Decodable] {
+        return self.filter({ $0.encoded != nil }).map({ $0.encoded! })
+    }
+}
+
+
+extension Sequence where Iterator.Element: Decodable {
+    var decoded: [Encodable] {
+        return self.filter({ $0.decoded != nil }).map({ $0.decoded! })
+    }
+}
diff --git a/Session.swift b/Session.swift
@@ -0,0 +1,59 @@
+public struct Session {
+    public internal(set) var startTime: Date
+    public internal(set) var endTime: Date?
+    public internal(set) var events: [Event]
+
+    public init(startTime: Date, endTime: Date?) {
+        self.startTime = startTime
+        self.endTime = endTime
+        self.events = []
+    }
+}
+
+extension Session {
+    class Coding: NSObject, NSCoding {
+        let session: Session?
+
+        init(session: Session) {
+            self.session = session
+            super.init()
+        }
+
+        required init?(coder aDecoder: NSCoder) {
+            guard let startTime = aDecoder.decodeObject(forKey: "startTime") as? Date,
+                let endTime = aDecoder.decodeObject(forKey: "endTime") as? Date?,
+                let events = aDecoder.decodeObject(forKey: "events") as? [Event.Coding] else {
+                    return nil
+            }
+
+            var decodedSession = Session(startTime: startTime, endTime: endTime)
+            decodedSession.events = events.decoded as! [Event]
+            session = decodedSession
+
+            super.init()
+        }
+
+        public func encode(with aCoder: NSCoder) {
+            guard let session = session else {
+                return
+            }
+
+            aCoder.encode(session.startTime, forKey:"startTime")
+            aCoder.encode(session.endTime, forKey:"endTime")
+            aCoder.encode(session.events.encoded, forKey:"events")
+        }
+    }
+}
+
+
+extension Session: Encodable {
+    var encoded: Decodable? {
+        return Session.Coding(session: self)
+    }
+}
+
+extension Session.Coding: Decodable {
+    var decoded: Encodable? {
+        return self.session
+    }
+}
diff --git a/main.swift b/main.swift
@@ -0,0 +1,29 @@
+var session1 = Session(startTime: Date(), endTime: Date())
+session1.events.append(Event(timeStamp: Date(), tag: "test session1/event1"))
+session1.events.append(Event(timeStamp: Date(), tag: "test session1/event2"))
+var session2 = Session(startTime: Date(), endTime: Date())
+session2.events.append(Event(timeStamp: Date(), tag: "test session2/event1"))
+session2.events.append(Event(timeStamp: Date(), tag: "test session2/event2"))
+session2.events.append(Event(timeStamp: Date(), tag: "test session2/event3"))
+let sessions: [Session] = [session1, session2]
+
+let data = NSKeyedArchiver.archivedData(withRootObject: sessions.encoded)
+let back = (NSKeyedUnarchiver.unarchiveObject(with: data) as? [Session.Coding])?.decoded
+print(back ?? "error in getting back sessions")
+
+/*
+[
+  Session(
+    startTime: 2016-10-15 13:34:45 +0000, 
+    endTime: Optional(2016-10-15 13:34:45 +0000), 
+    events: [
+      Event(timeStamp: 2016-10-15 13:34:45 +0000, eventTag: "test session1/event1"), 
+      Event(timeStamp: 2016-10-15 13:34:45 +0000, eventTag: "test session1/event2")]), 
+  Session(
+    startTime: 2016-10-15 13:34:45 +0000, 
+    endTime: Optional(2016-10-15 13:34:45 +0000), 
+    events: [
+      Event(timeStamp: 2016-10-15 13:34:45 +0000, eventTag: "test session2/event1"), 
+      Event(timeStamp: 2016-10-15 13:34:45 +0000, eventTag: "test session2/event2"), 
+      Event(timeStamp: 2016-10-15 13:34:45 +0000, eventTag: "test session2/event3")])]
+*/
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