Cfdictionary Get Value for Key in Swift3

CFDictionary get Value for Key in Swift3

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)
            }
        }
    }
}

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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)
            }
        }
    }
}

How to access CFDictionary in Swift 3?

If you don't have to deal with other Core Foundation functions expecting an CFDictionary, you can simplify it by converting to Swift native Dictionary:

if let dict = cfDict as? [String: AnyObject] {
    print(dict["key"])
}

pass dictionary key to CFDictionaryGetValue

The easiest solution is to take advantage of the toll-free bridging
between CFDictionary and NSDictionary, and use the NSDictionary
accessor methods:

let ds = SCDynamicStoreCreate(nil, "setNet", nil, nil)!

if let list = SCDynamicStoreCopyProxies(ds) as NSDictionary? {
    if let port = list[kSCPropNetProxiesHTTPPort as NSString] as? Int {
        print("HTTPPort:", port)
    }
}

But just for the sake of completeness: It can be done with
CFDictionaryGetValue:

if let list = SCDynamicStoreCopyProxies(ds)  {
    let key = kSCPropNetProxiesHTTPPort
    let port = unsafeBitCast(CFDictionaryGetValue(list, unsafeAddressOf(key)), NSObject!.self)
    if port != nil {
        print("HTTPPort:", port)
    }
}

Cannot access CFDictionary elements from Swift3

To fix your specific problem, replace metadata as? [String:Any]["{Exif}"] with (metadata as! [String:Any])["{Exif}"] The problem you are encountering is that metadata as? [String:Any] is of type [String: Any]?, since you are using the conditional cast as!.

However, the idiomatic way to do this in Swift is to use guard-let statements like so:

guard let metadata:CFDictionary = CGImageSourceCopyPropertiesAtIndex(source!,0,nil) else {
    fatalError("Cannot get image properties!")
}

guard let dictionary = metadata as? [String: Any] else {
    fatalError("Cannot convert metadata to dictionary!")
}

guard let exifData = dictionary["{Exif}"] as? [SomeCFType: Int] else { //I'm not sure what type PixelXDimension, PixelYDimension, and ColorSpace are
    fatalError("Cannot get EXIF data!")
}

Swift 3 - Working with UnsafePointerCFDictionary?

Swift's CFDictionary isn't itself a data structure; it's a pointer to a data structure, and it is equivalent to Objective-C's CFDictionaryRef. In other words, it behaves like a Swift class, not a struct.

The value written into outDataPointer is not a pointer to a CFDictionary; it is a CFDictionary. You're dereferencing it one too many times, causing the data stored in the dictionary to be treated as a pointer to a dictionary. On my system, the resulting memory address was 0x001dffffc892e2f1, which Objective-C treats as a tagged pointer, resulting in the NSAtom message.

To fix the problem, declare outDataPointer as a CFDictionary? instead of an UnsafePointer<CFDictionary>?:

// Get metadata
var outDataPointer: CFDictionary? = nil

possibleError = AudioFileGetProperty(audiofile!, kAudioFilePropertyInfoDictionary, &outDataSize, &outDataPointer)
assert(possibleError == noErr)

let outData = outDataPointer! as NSDictionary
dump(outData)

Output:

▿ 1 key/value pair #0
  ▿ (2 elements)
    - .0: approximate duration in seconds #1
      - super: __NSCFString
        - super: NSMutableString
          - super: NSString
            - super: NSObject
    - .1: 187.387 #2
      - super: NSString
        - super: NSObject

Cast Swift Dictionary to CFDictionary

Yes you can do that. your solution will work and you can also do it like this.

var dictionary = [

    key:value

] as CFDictionary

You can refer further from here

Swift 3 - Trying to cast a dictionary to CFDictionary

You can use below code to convert the dictionary to CFDictionary as mention below:

let attrs = [kCVPixelBufferCGImageCompatibilityKey as String :kCFBooleanTrue,
             kCVPixelBufferCGBitmapContextCompatibilityKey as String:kCFBooleanTrue] as
        CFDictionary

Hope This will helps

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