Swift2：初始化 UnsafeMutablePointer<Unmanaged<CFMutableDictionary>?> 参数以传递给 IORegistryEntryCreateCFProperties 的正确方法

Question

好的，所以在Swift2中，IORegistryEntryCreateCFProperties的定义是

func IORegistryEntryCreateCFProperties(entry: io_registry_entry_t, _ properties: UnsafeMutablePointer<Unmanaged<CFMutableDictionary>?>, _ allocator: CFAllocator!, _ options: IOOptionBits) -> kern_return_t

我能做到

var dict: UnsafeMutablePointer<Unmanaged<CFMutableDictionary>?> = nil
kr = IORegistryEntryCreateCFProperties(box as io_registry_entry_t, dict, kCFAllocatorDefault, nilOptions)

编译运行。当然它在执行 IORegistryEntryCreateCFProperties 时会崩溃，因为 dict 被初始化为 nil。我的问题是如何将 dict 初始化为非零值？我试过各种方法都没有成功。

Answer 1

类型的参数

UnsafeMutablePointer<Unmanaged<CFMutableDictionary>?>

意味着你必须传递一个

类型的变量

Unmanaged<CFMutableDictionary>?

作为 & 的输入参数。成功后，您可以打开可选的（带有可选的绑定），将非托管对象转换为托管对象 takeRetainedValue()，最后（如果需要），将 CFMutableDictionary 转换为 NSDictionary。

示例：

var props : Unmanaged<CFMutableDictionary>?
if IORegistryEntryCreateCFProperties(entry, &props, kCFAllocatorDefault, 0) == KERN_SUCCESS {
    if let props = props {
        let dict = props.takeRetainedValue() as NSDictionary
        print(dict)
    }
}

Swift2：初始化 UnsafeMutablePointer<Unmanaged<CFMutableDictionary>?> 参数以传递给 IORegistryEntryCreateCFProperties 的正确方法

Swift2: Correct way to initialise UnsafeMutablePointer<Unmanaged<CFMutableDictionary>?> parameter to pass to IORegistryEntryCreateCFProperties

macos

iokit

swift

swift2