如何傳遞UnsafeMutablePointer類型的參數<UnsafePointer <Void>>

Question

我必須在Swift中使用CFDictionaryCreate方法（documentation link）。

我很難正確初始化輸入參數以便傳遞UnsafeMutablePointer<UnsafePointer<Void>>類型的參數（鍵和值）。

這裏是我的代碼：

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

您可以簡單地使用[ NSString : AnyObject ]型，它是自動橋接NSDictionary或 CFDictionary的斯威夫特字典。請注意，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) 

另外，

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

因爲NSAttributedString是免費電話與 CFAttributedString橋接。

---

只是爲了完整起見，這裏是你如何使用 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)