How to encode Int as an optional using NSCoding
If it can be optional, you will have to use encodeObject for it, too.
You are using an Objective-C framework and Objective-C allows nil only for objects (class/reference types). An integer cannot be nil in Objective-C.
However, if you use encodeObject, Swift will automatically convert your Int to NSNumber, which can be nil.
Another option is to skip the value entirely:
if let myIntValue = myInt { aCoder.encodeInteger(myIntValue, forKey: "MyInt")}and use containsValueForKey(_:) when decoding.