在Swift中将字符串写入NSOutputStream [英] Writing a String to an NSOutputStream in Swift

问题描述

我正在尝试在Swift中将String写入NSOutputStream.使用Objective C编写字符串通常可以通过将其作为NSData传递来实现.

I'm trying to write a String to an NSOutputStream in Swift. Writing Strings that way with Objective C usually works by passing it as NSData

NSData *data = [[NSData alloc] initWithData:[mystring dataUsingEncoding:NSASCIIStringEncoding]];
[outputStream write:[data bytes] maxLength:[data length]];

这不适用于迅速

var data: NSData = mystring.dataUsingEncoding(NSUTF8StringEncoding)!
outputStream.write(data, maxLength: data.length)

这会产生错误

'NSData'不能转换为'UnsafePointer'

'NSData' is not convertible to 'UnsafePointer'

用于将数据写入流的行.

for the line that writes the data to the stream.

如何在Swift中将字符串写入NSOutputStream?

How would you write a String to an NSOutputStream in Swift?

推荐答案

这里有两个问题.首先是您要将data传递给outputStream.write()而不是data.bytes(就像您在Objective-C代码中传递了[data bytes]一样).第二个问题是data.bytes返回UnsafePointer<Void>，但是NSOutputStream.write()接受UnsafePointer<UInt8>.幸运的是，UnsafePointer可以在类型之间进行转换:

There are two issues here. The first is that you're passing data to outputStream.write() and not data.bytes (like you passed [data bytes] in your Objective-C code). The second issue is that data.bytes returns an UnsafePointer<Void>, but NSOutputStream.write() takes an UnsafePointer<UInt8>. Luckily, UnsafePointer has a way to convert between types:

/// Convert from a UnsafePointer of a different type.
///
/// This is a fundamentally unsafe conversion.
init<U>(_ from: UnsafePointer<U>)

将这些内容放在一起会使您的代码看起来像这样:

Putting those things together makes your code look something like this:

let data: NSData = mystring.dataUsingEncoding(NSUTF8StringEncoding)!
outputStream.write(UnsafePointer<UInt8>(data.bytes), maxLength: data.length)

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