How to Convert a Swift String to Cfstring

How to convert a swift String to CFString

Just cast it:

var str = "Hello, playground" as CFString
NSString(format: "type id: %d", CFGetTypeID(str))

Note that you'll need import Foundation for cast as CFString to work.

Otherwise if you only have import CoreFoundation, you'll need to force cast as! CFString.

How to convert String to CFMutableString?

Most immutable classes in Cocoa has a mutableCopy() method to return a mutable clone of itself. NSString.mutableCopy() returns an NSMutableString. NSData.mutableCopy() returns an NSMutableData, etc.

You can then bridge from Cocoa (NS*) to Foundation (CF*) class:

let str = "Hello world"
let cfString = (str as NSString).mutableCopy() as! CFMutableString

How to convert a String type variable to CFString in Swift?

Swift.String and NSString bridge automatically, and NSString and CFString can be cast to one another, but you can't (for now?) transitively get all the way from a Swift String to a CFString without an extra cast or two.

Here's a Swift string, a function that takes a CFString, and how to call it by casting to NSString:

var str = "Hello, playground"

func takesCFString(s: CFString) {}

takesCFString(str as NSString)

Note you don't need to use CFStringRefin Swift (and most of the Swift declarations of CFString API don't). The compiler takes advantage of the automatic ARC bridging for CF types that was introduced with Xcode 5 to let you treat those types like Swift (or ObjC) objects.

How to cast between CFString and String with swift on linux

As far as I tried on the IBM Swift Sandbox, CFStringTransform does not work on arbitrary CFMutableStrings. Seems it requires CFMutableString based on UTF-16 representation.

import Foundation
#if os(Linux)
    import CoreFoundation
    import Glibc
#endif
public extension String {
    func transformToLatinStripDiacritics() -> String{
        let chars = Array(self.utf16)
        let cfStr = CFStringCreateWithCharacters(nil, chars, self.utf16.count)
        let str = CFStringCreateMutableCopy(nil, 0, cfStr)!
        if CFStringTransform(str, nil, kCFStringTransformToLatin, false) {
            if CFStringTransform(str, nil, kCFStringTransformStripDiacritics, false) {
                return String(describing: str)
            }
            return self
        }
        return self
    }
}

print("我在大阪住".transformToLatinStripDiacritics()) //->wo zai da ban zhu

Tested only for a few examples. So, this may not be the best solution for your issue.

CFString convert to String for kUTTypeImage in Swift 2.0 & XCODE 7

From the header file:

public var mediaTypes: [String]
// default value is an array containing kUTTypeImage.

So you can actually just delete that line.

But if you want to keep it, you just need to be explicit that you want a cast:

picker.mediaTypes = [kUTTypeImage as String]

Avoiding forced downcast from Any to CFString

Import Foundation to give the compiler information about bridging between Core Foundation types and Foundation types. Then cast the array as you want:

import Foundation
import SystemConfiguration.CaptiveNetwork

func fetchSSIDInfo() -> String? {
    var ssid: String?
    if let interfaces = CNCopySupportedInterfaces() as? [CFString] {
        for interface in interfaces {
            if let interfaceInfo = CNCopyCurrentNetworkInfo(interface) as NSDictionary? {
                ssid = interfaceInfo[kCNNetworkInfoKeySSID as String] as? String
                break
            }
        }
    }
    return ssid
}

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