在Swift中从NSData中提取结构 [英] Extract struct from NSData in Swift

问题描述

我正在制作Game Center游戏.我发送一个包含struct MovePacket的数据包，如下所示:

I'm making Game Center game. I send a data packet containing a struct MovePacket like this:

var packet = MovePacket(packetID: 1, move: myMove)

let dataPacket = NSData(bytes: &packet, length: sizeof(MovePacket))

currentMatch!.sendDataToAllPlayers(dataPacket, withDataMode: GKMatchSendDataMode.Reliable, error: nil)

这就像在Objective-C中一样，但是我不明白如何将接收到的NSData解码回我的struct MovePacket.这是我的尝试之一:

This works like in Objective-C, but I don't understand how to decode the received NSData back to my struct MovePacket. This is one of my tries:

func match(match: GKMatch!, didReceiveData data: NSData!, fromRemotePlayer player: GKPlayer!) {

    var packet : MovePacket 

    data.getBytes(&packet, length: sizeof(MovePacket)) // getting error here: Address of variable 'packet' taken before it is initialized

    println(packet) //Variable 'packet' used before being initialized

}

推荐答案

假设您的意思是将其从 NSData 解码回":

Assuming you meant "decode it back from NSData":

func match(match: GKMatch!, didReceiveData data: NSData!, fromRemotePlayer player: GKPlayer!) {
    if data.length == sizeof(MovePacket) {
        let packet = UnsafePointer<MovePacket>(data.bytes).memory
        println(packet)
    } else {
        // error: data size is incorrect
    }
}

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