How to convert an Int into NSData in Swift?

Question

In Objective-C I use the following code to

1. Convert an Int variable into NSData, a packet of bytes.

   int myScore = 0;
   NS         
   
   
           

Answer 1

In contemporary versions of Swift, I would do:

let score = 1000
let data = withUnsafeBytes(of: score) { Data($0) }

e8 03 00 00 00 00 00 00 

And convert that Data back to an Int:

let value = data.withUnsafeBytes {
    $0.load(as: Int.self)
}

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Note, when dealing with binary representations of numbers, especially when exchanging with some remote service/device, you might want to make the endianness explicit, e.g.

let data = withUnsafeBytes(of: score.littleEndian) { Data($0) }

 e8 03 00 00 00 00 00 00 

And convert that Data back to an Int:

let value = data.withUnsafeBytes {
    $0.load(as: Int.self).littleEndian
}

Versus big endian format, also known as “network byte order”:

let data = withUnsafeBytes(of: score.bigEndian) { Data($0) }

 00 00 00 00 00 00 03 e8

And convert that Data back to an Int:

let value = data.withUnsafeBytes {
    $0.load(as: Int.self).bigEndian
}

Needless to say, if you don’t want to worry about endianness, you could use some established standard like JSON (or even XML).

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For Swift 2 rendition, see previous revision of this answer.