CFDictionary 获取 Swift3 中键的值

Question

我在访问 CFDictionary 中的特定（或任何）键时遇到问题。老实说，在 Swift 中，我并没有真正理解您需要执行此操作的方式，而且我认为它过于复杂...

我的代码：

if let session = DASessionCreate(kCFAllocatorDefault) {
let mountedVolumes = FileManager.default.mountedVolumeURLs(includingResourceValuesForKeys: [], options: [])!
for volume in mountedVolumes {
    if let disk = DADiskCreateFromVolumePath(kCFAllocatorDefault, session, volume as CFURL) {
        let diskinfo = DADiskCopyDescription(disk);   

        var volumeValue = CFDictionaryGetValue(diskinfo, <#T##key: UnsafeRawPointer!##UnsafeRawPointer!#>)


    }
}

我想要实现的目标：将键或字段 DAVolumeNetwork 的值获取到变量 volumeValue 中。我想我需要将 kDADiskDescriptionVolumeNetworkKey 传递给 CFDictionaryGetValue 方法？我该如何实现？

Answer 1

不要在 Swift 中使用 CFDictionary。（这是可能的，但不值得，见下文。）

CFDictionary 是免费电话与 NSDictionary 桥接，后者又可以转换为 Swift Dictionary.
kDADiskDescriptionVolumeNetworkKey键的值是 CFBoolean 可以转换为 Swift Bool.

示例：

if let session = DASessionCreate(kCFAllocatorDefault),
    let mountedVolumes = FileManager.default.mountedVolumeURLs(includingResourceValuesForKeys: []) {
    for volume in mountedVolumes {
        if let disk = DADiskCreateFromVolumePath(kCFAllocatorDefault, session, volume as CFURL),
            let diskinfo = DADiskCopyDescription(disk) as? [NSString: Any] {

            if let networkValue = diskinfo[kDADiskDescriptionVolumeNetworkKey] as? Bool {
                print(networkValue)
            }
        }
    }
}

为了完整起见：这是必要的指针在 Swift 3:

中调用 CFDictionaryGetValue

if let session = DASessionCreate(kCFAllocatorDefault),
    let mountedVolumes = FileManager.default.mountedVolumeURLs(includingResourceValuesForKeys: []) {
    for volume in mountedVolumes {
        if let disk = DADiskCreateFromVolumePath(kCFAllocatorDefault, session, volume as CFURL),
            let diskinfo = DADiskCopyDescription(disk) {

            if let ptr = CFDictionaryGetValue(diskinfo, Unmanaged.passUnretained(kDADiskDescriptionVolumeNetworkKey).toOpaque()) {
                let networkValue = Unmanaged<NSNumber>.fromOpaque(ptr).takeUnretainedValue()
                print(networkValue.boolValue)
            }
        }
    }
}

Answer 2

您可以将 CFDictionaryRef 转换为 Swift 字典：

if let disk = DADiskCreateFromVolumePath(kCFAllocatorDefault, session, volume as CFURL), let diskinfo = DADiskCopyDescription(disk) as? [String: AnyObject] {
}

然后将 kDADiskDescriptionVolumeNetworkKey 转换为 Swift 字符串：

var volumeValue = diskinfo[kDADiskDescriptionVolumeNetworkKey as String]

CFDictionary 获取 Swift3 中键的值

CFDictionary get Value for Key in Swift3

swift

cfdictionary