iOS Swift How do you Secure Encode/Decode a TimeInterval for compatibility with NSSecureCoding?

Question

I have a variable

var pausedTime: TimeInterval?

I want to encode & decode it with NSSecureCoding

So far I have this for encoding:

aCoder.encode(pausedTime, forKey: "Pause")

and this for decoding, treating the TimeInterval as a Double:

if aDecoder.containsValue(forKey: "Pause") {
    pausedTime = aDecoder.decodeDouble(forKey: "Pause")
}

But this is not working and resulting in the error:

[error] fault: exception raised during multi-threaded fetch *** -[NSKeyedUnarchiver decodeDoubleForKey:]: value for key (pausedTime) is not a 64-bit float ({ "__NSCoderInternalErrorCode" = 4864; })

Please could someone provide me with the correct way to secure encode/decode a TimeInterval?

Answer 1

First, TimeInterval is exactly a Double (it's just a typealias). This is useful to know in case you expect any specialness about TimeInterval. There isn't any.

In your case, pausedTime is not a TimeInterval, however. It's a TimeInterval?. You're probably winding up calling the encode(Any?, forKey:) overload, and that's probably boxing your double into an NSNumber.

To fix that, you should make sure you're encoding a Double. For example:

if let pausedTime = pausedTime {
   aCoder.encode(pausedTime, forKey: "Pause")
}

or

aCoder.encode(pausedTime ?? 0.0, forKey: "Pause")