如何传递类型为不安全的可变指针<不安全指针<Void>>

Question

我必须在swift（文档链接）中使用 CFDictionaryCreate方法。

我很难正确地初始化输入参数，以便通过类型UnsafeMutablePointer<UnsafePointer<Void>>的参数（键和值）。

这是我的代码：

    var font_name: CFStringRef! = CFStringCreateWithCString(nil, "Courier", kCFStringEncodingASCII)
    var font: CTFontRef! = CTFontCreateWithName(font_name, 25.0, nil)
    var keys: [UnsafePointer<Void>] = ???? // how to intialize with "kCTFontAttributeName"
    var values: [UnsafePointer<Void>] = ???? // how to intialize with "font" variable
    var keyCallBacks = kCFTypeDictionaryKeyCallBacks
    var valueCallBacks = kCFTypeDictionaryValueCallBacks
    var font_attributes: CFDictionaryRef! = CFDictionaryCreate(kCFAllocatorDefault,   &keys, &values, sizeofValue(keys), &keyCallBacks, &valueCallBacks)
    var attr_string: CFAttributedStringRef! = CFAttributedStringCreate(nil, "hello", font_attributes)

Answer 1

您可以简单地使用[ NSString : AnyObject ]类型的Swift字典，该字典自动桥接到NSDictionary或 CFDictionary。请注意，您也不需要CFStringRef。

let font = CTFontCreateWithName("Courier", 25.0, nil)
let attributes : [ NSString : AnyObject ] = [ kCTFontAttributeName : font ]
let attrString = CFAttributedStringCreate(nil, "Hello", attributes)

或者，

let attrString = NSAttributedString(string: "Hello", attributes: attributes)

因为 NSAttributedString是免费的 CFAttributedString。

---

只是为了完整，这是您可以使用的方式 CFDictionaryCreate()：

let font = CTFontCreateWithName("Courier", 25.0, nil)
var keys = [ unsafeAddressOf(kCTFontAttributeName) ]
var values = [ unsafeAddressOf(font) ]
var keyCallbacks = kCFTypeDictionaryKeyCallBacks
var valueCallbacks = kCFTypeDictionaryValueCallBacks
let attributes = CFDictionaryCreate(nil, &keys, &values, 1, &keyCallbacks, &valueCallbacks)
let attrString = CFAttributedStringCreate(nil, "Hello", attributes)