如何在 OS X 目标中创建 CFDictionary？

Question

根据文档，CFDictionaryCreate被用于Swift中实例化CFDictionary。

func CFDictionaryCreate(_ allocator: CFAllocator!,
                  _ keys: UnsafeMutablePointer<UnsafePointer<Void>>,
                  _ values: UnsafeMutablePointer<UnsafePointer<Void>>,
                  _ numValues: CFIndex,
                  _ keyCallBacks: UnsafePointer<CFDictionaryKeyCallBacks>,
                  _ valueCallBacks: UnsafePointer<CFDictionaryValueCallBacks>) -> CFDictionary!

我该如何创建 keys 和 values 参数？ 目前，我尝试使用Swift的 String 类型，希望它能自动转换为适当的类型：

import Foundation

var keys : [String] = ["key1", "key2"]
var values : [String] = ["value1", "value2"]
var keyCallbacks = kCFTypeDictionaryKeyCallBacks
var valueCallbacks = kCFTypeDictionaryValueCallBacks
var dict : CFDictionary = CFDictionaryCreate(kCFAllocatorDefault,
    &keys, &values, 2, &keyCallbacks, &valueCallbacks)

不幸的是，我收到了一个错误提示，说String不是keys和values数组元素的正确类型：

main.swift:41:2: error: 'String' is not identical to 'UnsafePointer<Void>'
    &configKeys, &configValues, 3, &keyCallbacks, &valueCallbacks)

我如何从 String 创建一个 UnsafePointer<Void>？

- PovilasB

---

最简单的方法是 let dict:CFDictionary = ["key1":"value1", "key2":"value2"] :) - rintaro

那个可以工作，谢谢 :) - PovilasB

Answer 1

对于Swift 3，您需要进行额外的类型转换以使用CFDictionary。否则，会抛出“无法将上下文类型'CFDictionary'与字典文字一起使用”的错误。

let options: CFDictionary = [kSecImportExportPassphrase as String : "certificateKey"] as CFDictionary

更多信息请参见https://bugs.swift.org/browse/SR-2388

- Kildyt

Answer 2

Printaro的评论适用于字符串字面量，但是当我使用CFStringRef和Swift String时不起作用：

// Error: Contextual type 'CFDictionary' cannot be used with dictionary literal
let options: CFDictionary = [kSecImportExportPassphrase : "certificateKey"]

我需要将CFStringRef强制转换为Swift String:

let options: CFDictionary = [kSecImportExportPassphrase as String : "certificateKey"] // works

- JAL