xcode - 在 Xcode Playground 中将 NSString 转换为 CString

Question

当我尝试时:

import Cocoa
var ns: NSString = "whatever"
var cs: CString = ns.UTF8String
println(cs)

在 Playground 中，它在执行 var cs: CString = ns.UTF8String 语句时报告此异常:

fatal error: Can't unwrap Optional.None
Playground execution failed: error: Execution was interrupted, reason: EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0).
The process has been left at the point where it was interrupted, use "thread return -x" to return to the state before expression evaluation.
* thread #1: tid = 0xbf05a5, 0x000000010401b02d libswift_stdlib_core.dylib`Swift._StringCore._growBuffer (@inout Swift._StringCore)(Swift.Int, minElementWidth : Swift.Int) -> Swift.COpaquePointer + 813, queue = 'com.apple.main-thread', stop reason = EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0)
  * frame #0: 0x000000010401b02d libswift_stdlib_core.dylib`Swift._StringCore._growBuffer (@inout Swift._StringCore)(Swift.Int, minElementWidth : Swift.Int) -> Swift.COpaquePointer + 813
    frame #1: 0x000000010401643f libswift_stdlib_core.dylib`Swift._StringCore.append (@inout Swift._StringCore)(Swift._StringCore) -> () + 607
    frame #2: 0x0000000104016fa5 libswift_stdlib_core.dylib`Swift.+ @infix (Swift.String, Swift.String) -> Swift.String + 117
...truncated...

但是，相同的代码在编译到应用程序中时会按预期工作。它看起来像一个 Playground 错误，但有人知道在 Playground 中将 NSString 转换为 Cstring 的解决方法吗？

Answer 1

通过将 cs 设为 CString 可选，我能够让它在 Playground 上工作。

import Cocoa
var ns: NSString = "whatever"
println(ns)
var cs: CString? = ns.UTF8String
println(cs)

如果你需要打开可选的

if let str = cs{
println(str)
}