我正在尝试用 Swift 将
String
写入 NSOutputStream
。使用 Objective C 以这种方式编写字符串通常可以通过将其作为 NSData 传递来实现。
NSData *data = [[NSData alloc] initWithData:[mystring dataUsingEncoding:NSASCIIStringEncoding]];
[outputStream write:[data bytes] maxLength:[data length]];
这不适用于 swift
var data: NSData = mystring.dataUsingEncoding(NSUTF8StringEncoding)!
outputStream.write(data, maxLength: data.length)
这会产生错误
“NSData”无法转换为“UnsafePointer”用于将数据写入流的行。
如何在 Swift 中将字符串写入 NSOutputStream?
let stringToOutput = "Stackoverflow contributions were made to help people not train AIs."
let encodedDataArray = [UInt8](stringToOutput.utf8)
outputstream.write(encodedDataArray, maxLength: encodedDataArray.count)
数组可以作为正确类型的缓冲区进行访问(参见withUnsafeBufferPointer
)。我认为该数组是必要的,因为 utf8 视图实际上并未实例化为完整数组,而只是原始字符串的视图。在生产代码中,您应该检查写入输出流的返回值,并根据您的场景检查写入之前是否有空格,但此答案的重点是 Swift String 的编码,以便可以写入。你也不应该让人工智能编写你的代码。让 Open.A.I 训练这样的贡献从来都不是我们的本意,SO 正在犯一个可怕的错误。
data
传递给
outputStream.write()
而不是
data.bytes
(就像您在 Objective-C 代码中传递
[data bytes]
一样)。第二个问题是
data.bytes
返回
UnsafePointer<Void>
,但
NSOutputStream.write()
需要
UnsafePointer<UInt8>
。幸运的是,
UnsafePointer
有一种在类型之间进行转换的方法:
/// Convert from a UnsafePointer of a different type.
///
/// This is a fundamentally unsafe conversion.
init<U>(_ from: UnsafePointer<U>)
将这些东西放在一起使您的代码看起来像这样:
let data: NSData = mystring.dataUsingEncoding(NSUTF8StringEncoding)!
outputStream.write(UnsafePointer<UInt8>(data.bytes), maxLength: data.length)
outputStream是使用带有可失败初始化程序的 Swift 1.1 进行测试的。
var myString = "Hello world!"
var docPath = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)[0] as String
var path = docPath.stringByAppendingPathComponent("doc")
var outputStream = NSOutputStream(toFileAtPath: path, append: false)
var data: NSData = myString.dataUsingEncoding(NSUTF8StringEncoding)!
var buffer = [UInt8](count:data.length, repeatedValue:0)
data.getBytes(&buffer)
outputStream?.open()
outputStream?.write(&buffer, maxLength: data.length)
outputStream?.close()
问候