Cocoa异步套接字教程代码从Swift 2转换为Swift 3

Question

I am working through a Swift 2 Cocoa Async Socket tutorial which was downloaded from https://github.com/nickyhuyskens/SwiftCocoaAsyncSocketTutorial It was written in Swift 2 and I am working with Xcode 8 / Swift 3. The conversion seem fairly good with only a few correction except for one place where I cannot seem to make the needed correction.

Original Swift 2 code:

func socket(_ sock: GCDAsyncSocket!, didRead data: Data!, withTag tag: Int)
 {
    if tag == 1 {
         var bodyLength: Int16 = 0
         data.getBytes(&bodyLength, length: sizeof(Int16))
         print("Header received with bodylength: \(bodyLength)")
         socket.readDataToLength(UInt(bodyLength), withTimeout: -1, tag: 2)
    } else if tag == 2 {             
         let packet = NSKeyedUnarchiver.unarchiveObjectWithData(data) as! Packet
         PacketHandler.HandlePacket(packet)
         socket.readDataToLength(UInt(sizeof(Int16)), withTimeout: -1, tag: 1)
        socket.readData(toLength: UInt(MemoryLayout<Int16>.size), withTimeout: -1, tag: 1)
    }
}

My Swift 3 changes:

func socket(_ sock: GCDAsyncSocket!, didRead data: Data!, withTag tag: Int) {
   if tag == 1 {
                    var bodyLength: UInt16 = 0
        bodyLength = (UInt16(MemoryLayout<Data>.size))
        print("Header received with bodylength: \(bodyLength)")
        socket.readData(toLength: UInt(bodyLength), withTimeout: -1, tag: 2)
    } else if tag == 2 {
        let packet = NSKeyedUnarchiver.unarchiveObject(with: data) as! Packet
        PacketHandler.HandlePacket(packet)
        socket.readData(toLength: UInt(MemoryLayout<Int16>.size), withTimeout: -1, tag: 1)
    }
}

When it gets to the line

let packet = NSKeyedUnarchiver.unarchiveObject(with: data) as! Packet

the result is a "fatal error: unexpectedly found nil while unwrapping an Optional value". I have been looking at posts involving the changes in Swift 3 around change to getting the "sizeof" data and am not sure if the change to "MemoryLayout" was correct. Also I have tried a number of changes following posts involving Swift 3 changes to the use of the NSKeyedUnarchiver.unarchiveObjectWithData functionality but those also do not provide a working solution.

Any assistance or pointing to where the conversion solution can be found would be greatly appreciated.

Answer 1

print(MemoryLayout<Data>.size == 8)

prints

true

Are You sure that this is what do You expect? It is the size of Data type, not the number of stored bytes.

the size of data (for example)

let data = Data(bytes: [1,2,3,4,5,6,7,8,9,0])
print(data.count)

prints

10