ios 如何在 Swift 中将 Int 转换为 NSData？
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How to convert an Int into NSData in Swift?
提问by Cesare
In Objective-C I use the following code to
在 Objective-C 中，我使用以下代码
Convert an
Intvariable intoNSData, a packet of bytes.int myScore = 0; NSData *packet = [NSData dataWithBytes:&myScore length:sizeof(myScore)];Use the converted
NSDatavariable into a method.[match sendDataToAllPlayers: packet withDataMode: GKMatchSendDataUnreliable error: &error];
将一个
Int变量转换为NSData一个字节包。int myScore = 0; NSData *packet = [NSData dataWithBytes:&myScore length:sizeof(myScore)];将转换后的
NSData变量用于方法。[match sendDataToAllPlayers: packet withDataMode: GKMatchSendDataUnreliable error: &error];
I tried converting the Objective-C code into Swift:
我尝试将 Objective-C 代码转换为 Swift：
var myScore : Int = 0
func sendDataToAllPlayers(packet: Int!,
withDataMode mode: GKMatchSendDataMode,
error: NSErrorPointer) -> Bool {
return true
}
However, I am not able to convert an Intvariable into an NSDataand use it an a method. How can I do that?
但是，我无法将Int变量转换为 anNSData并将其用作 a 方法。我怎样才能做到这一点？
回答by Raphael
With Swift 3.x to 5.0:
使用 Swift 3.x 到 5.0：
var myInt = 77
var myIntData = Data(bytes: &myInt,
count: MemoryLayout.size(ofValue: myInt))
回答by Rob
In contemporary versions of Swift, I would do:
在当代版本的 Swift 中，我会这样做：
let score = 1000
let data = withUnsafeBytes(of: score) { Data(e8 03 00 00 00 00 00 00
) }
let value = data.withUnsafeBytes {
let data = withUnsafeBytes(of: score.littleEndian) { Data( e8 03 00 00 00 00 00 00
) }
.load(as: Int.self)
}
And convert that Databack to an Int:
并将其转换Data回一个Int：
let value = data.withUnsafeBytes {
let data = withUnsafeBytes(of: score.bigEndian) { Data( 00 00 00 00 00 00 03 e8
) }
.load(as: Int.self).littleEndian
}
Note, when dealing with binary representations of numbers, especially when exchanging with some remote service/device, you might want to make the endiannessexplicit, e.g.
请注意，在处理数字的二进制表示时，尤其是在与某些远程服务/设备交换时，您可能希望明确字节顺序，例如
let value = data.withUnsafeBytes {
var myScore: NSInteger = 0
let data = NSData(bytes: &myScore, length: sizeof(NSInteger))
.load(as: Int.self).bigEndian
}
let buffer = NSMutableData()
let size = MemoryLayout<UInt>.size
let big = 1000
let small = 10
withUnsafeBytes(of: big, { (p) in
let bufferPointer = p.bindMemory(to: UInt.self)
if let address = bufferPointer.baseAddress{
buffer.append(address, length: size)
}
})
withUnsafeBytes(of: small, { (p) in
let bufferPointer = p.bindMemory(to: UInt.self)
if let address = bufferPointer.baseAddress{
buffer.append(address, length: size)
}
})
And convert that Databack to an Int:
并将其转换Data回一个Int：
if let d = buffer.copy() as? Data{
var big: UInt = 0
var small: UInt = 0
let size = MemoryLayout<UInt>.size
let meta = NSData(data: data)
meta.getBytes(&big, range: NSRange(location: 0, length: size))
meta.getBytes(&small, range: NSRange(location: size, length: size))
print("big:", big, "\nsmall:", small)
// big: 1000
// small: 10
}
Versus big endian format, also known as “network byte order”:
与大端格式，也称为“网络字节顺序”：
##代码## ##代码##And convert that Databack to an Int:
并将其转换Data回一个Int：
Needless to say, if you don't want to worry about endianness, you could use some established standard like JSON (or even XML).
不用说，如果您不想担心字节顺序，您可以使用一些既定的标准，如 JSON（甚至 XML）。
For Swift 2 rendition, see previous revision of this answer.
对于 Swift 2 版本，请参阅此答案的先前修订版。
回答by David V
You can convert in this way:
您可以通过以下方式进行转换：
##代码##回答by dengST30
Swift 5, add an other option.
Swift 5，添加另一个选项。
NSDatais old, still effective
NSData是旧的，仍然有效
Write Data:
写入数据：
##代码##Read data:
读取数据：
##代码##You know the memory layout, the data put in the memory,
你知道内存布局，放入内存的数据，
Then put them out exactly.
然后把它们准确地放出来。
unsafemethod is funny
unsafe方法很有趣
