我正在尝试写一个程序,它将扫描可用的串行端口,并在弹出菜单中显示它们。为什么我不能直接从IORegistryEntryCreateCFProperty()
函数中获取CFString
,并通过下一行中的字符串插值将其添加到菜单中?由于某种原因,我的变量声明遇到以下错误:
"NSString不是CFString的子类型“。
import Foundation
import Cocoa
import IOKit
import IOKit.serial
@objc class Serial {
init() {
}
@IBOutlet var serialListPullDown : NSPopUpButton!
func refreshSerialList(defaultprompt: String) {
let masterPort: mach_port_t = kIOMasterPortDefault
let classesToMatch: CFDictionary = IOServiceMatching(kIOSerialBSDServiceValue).takeUnretainedValue()
var matchingServices: io_iterator_t = 0
// remove everything from the pull down list
serialListPullDown?.removeAllItems()
// ask for all the serial ports
let kernResult = IOServiceGetMatchingServices(masterPort, classesToMatch, &matchingServices)
if kernResult == KERN_SUCCESS {
// success
while (io_object_t() == IOIteratorNext(matchingServices)) {
var serialport = IORegistryEntryCreateCFProperty(io_object_t(), kIOCalloutDeviceKey, kCFAllocatorDefault, 0)
serialListPullDown?.addItemWithTitle("\(serialport)")
}
}
else {
// error
}
}
}
发布于 2014-08-18 03:13:26
Swift.String和NSString是免费桥接的。
NSString和CFString可以相互转换,但不能直接从Swift字符串转换为CFString,反之亦然。
按照以下步骤将Core Foundation字符串转换为Swift字符串:
var cfStr:CFString = "Soon, I'll be a Swift String"
var nsTypeString = cfStr as NSString
var swiftString:String = nsTypeString
CFTypeRef示例:
var cfStr:CFTypeRef = "Soon, I'll be a Swift String"
var nsTypeString = cfStr as NSString
var swiftString:String = nsTypeString
发布于 2015-10-24 02:15:30
至少从Swift 2.0 String
开始(从装有swift --version
的终端验证),您可以使用简单的String
as String
.将转换为本机Swift
这就足够了,因为任何需要NSString
的地方都可以使用Swift的String
类型。
一个带有kUTType*
常量的示例 (kUTType*
常量由CoreServices定义,并且是CFString
):
// Get UTF8 plain text from the pasteboard.
import AppKit
let str = NSPasteboard.generalPasteboard().stringForType(kUTTypeUTF8PlainText as String)
A更详细的示例
// Import at least the Foundation framework.
// Since Cocoa includes Foundation, `import Cocoa` works too.
// (Note that `import CoreServices`, even though it defines type `CFString`,
// is NOT enough - the conversion will fail.)
import Foundation
// Create a CFString.
// The fact that initializing from a `String` literal here works implies that
// the *reverse* cast - String -> CFString - also works.
var cfStr:CFString = "Cast me."
// Convert it to String.
var swiftStr = cfStr as String
要测试您正在处理的是哪种类型的:
cfStr is CFString // true
swiftStr is String // true
要使用获取字符串的类型,请使用.dynamicType
;在字符串上下文中,这将报告类型名称,但请注意,您可能会得到私有内部类的名称:
"cfStr is a \(cfStr.dynamicType) instance."
// -> "cfStr is a _NSContiguousString instance." !!
不过,正如上面的is
测试所示,您可以将其视为CFString
。
使用_stdlib_getDemangledTypeName()
获取真正的底层类名
_stdlib_getDemangledTypeName(cfStr) // -> "ObjectC.CFString"
_stdlib_getDemangledTypeName(kUTTypeUTF8PlainText) // ditto
发布于 2020-09-17 22:48:27
对我来说,我喜欢做一些扩展,然后再使用它们。阅读起来很方便,也很清楚:
扩展:
extension CFString {
var string: String {
return self as String
}
}
用法:
let specificQueryPart: [String: NSObject] = [
kSecReturnData.string: true as NSObject,
kSecAttrService.string: key as NSObject,
kSecMatchLimit.string: kSecMatchLimitOne
]
https://stackoverflow.com/questions/25351842
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