Swift相当于Objective-C FourCharCode单引号文字(例如'TEXT')

Question

我正在尝试在Swift中复制一些Objective C cocoa.一切都很好,直到我遇到以下情况:

// Set a new type and creator:
unsigned long type = 'TEXT';
unsigned long creator = 'pdos';

如何从单引号字符文字中创建Int64(或正确的Swift等价物)？

类型:

public typealias AEKeyword = FourCharCode
public typealias OSType = FourCharCode
public typealias FourCharCode = UInt32

Answer 1

我在我的Cocoa Scripting应用程序中使用它,它正确地认为字符> 0x80

func OSTypeFrom(string : String) -> UInt {
  var result : UInt = 0
  if let data = string.dataUsingEncoding(NSMacOSRomanStringEncoding) {
    let bytes = UnsafePointer<UInt8>(data.bytes)
    for i in 0..<data.length {
      result = result << 8 + UInt(bytes[i])
    }
  }
  return result
}

编辑:

另外

func fourCharCodeFrom(string : String) -> FourCharCode
{
  assert(string.count == 4, "String length must be 4")
  var result : FourCharCode = 0
  for char in string.utf16 {
    result = (result << 8) + FourCharCode(char)
  }
  return result
}

或者仍然更加迅速

func fourCharCode(from string : String) -> FourCharCode
{
  return string.utf16.reduce(0, {$0 << 8 + FourCharCode($1)})
}

Answer 2

我从 Swift API 中找到了以下类型别名：

typealias FourCharCode = UInt32
typealias OSType = FourCharCode

以及以下功能：

func NSFileTypeForHFSTypeCode(hfsFileTypeCode: OSType) -> String!
func NSHFSTypeCodeFromFileType(fileTypeString: String!) -> OSType

这应该允许我创建等效的代码：

let type : UInt32 = UInt32(NSHFSTypeCodeFromFileType("TEXT"))
let creator : UInt32 = UInt32(NSHFSTypeCodeFromFileType("pdos"))

但是那些 4 个字符的字符串不起作用并返回0.

如果将每个字符串用'单引号括起来'并调用相同的函数，您将获得正确的返回值：

let type : UInt32 = UInt32(NSHFSTypeCodeFromFileType("'TEXT'"))
let creator : UInt32 = UInt32(NSHFSTypeCodeFromFileType("'pdos'"))