CFDictionary get Value for Key in Swift3

问题

I've a problem with accessing a specific (or any) key in a CFDictionary. Honestly I don't really get the way you need to do this in Swift and I think it's overly complicated...

My Code:

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!#>)


    }
}

What I want to achieve: Get the Value for the Key or field DAVolumeNetwork into the variable volumeValue. I guess I need to pass the kDADiskDescriptionVolumeNetworkKey to the CFDictionaryGetValue Method? How do I achieve this?

回答1:

Don't use CFDictionary in Swift. (It is possible, but not worth the effort, see below.)

CFDictionary is toll-free bridged with NSDictionary, which in turn can be cast to a Swift Dictionary.
The value of the kDADiskDescriptionVolumeNetworkKey key is a CFBoolean which can be cast to a Swift Bool.

Example:

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)
            }
        }
    }
}

Just for the sake of completeness: This is the necessary pointer juggling to call CFDictionaryGetValue in Swift 3:

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)
            }
        }
    }
}

回答2:

You can cast CFDictionaryRef to a Swift dictionary:

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

and then cast kDADiskDescriptionVolumeNetworkKey to a Swift string:

var volumeValue = diskinfo[kDADiskDescriptionVolumeNetworkKey as String]

来源：https://stackoverflow.com/questions/42786613/cfdictionary-get-value-for-key-in-swift3

标签

swift

cfdictionary