Accessing temp directory in Swift - objective-c

Question

I was trying to access temp directory in Swift. In Objective-C, I could use the following code to do so:
- (NSString *)tempDirectory {
NSString *tempDirectoryTemplate =
[NSTemporaryDirectory() stringByAppendingPathComponent:#"XXXXX"];
const char *tempDirectoryTemplateCString = [tempDirectoryTemplate fileSystemRepresentation];
char *tempDirectoryNameCString = (char *)malloc(strlen(tempDirectoryTemplateCString) + 1);
strcpy(tempDirectoryNameCString, tempDirectoryTemplateCString);
char *result = mkdtemp(tempDirectoryNameCString);
if (!result) {
return nil;
}
NSString *tempDirectoryPath = [[NSFileManager defaultManager] stringWithFileSystemRepresentation:tempDirectoryNameCString length:strlen(result)];
free(tempDirectoryNameCString);
return tempDirectoryPath;
}
However, I'm a bit confuse about the type conversion and casting from Objective-C to Swift, such as const char * or CMutablePointer<CChar>. Is there any documents that I should look into?
Thanks.

Answer 1

How about something like :
public extension FileManager {
func createTempDirectory() throws -> String {
let tempDirectory = (NSTemporaryDirectory() as NSString).appendingPathComponent(UUID().uuidString)
try FileManager.default.createDirectory(atPath: tempDirectory,
withIntermediateDirectories: true,
attributes: nil)
return tempDirectory
}
}
It doesn't answer your question about char* but it's cleaner...
NSFileManager reference here.
Also check out this SO question regarding unique names.

Answer 2

According to Apple, use of NSTemporaryDirectory is discouraged:
See the FileManager method url(for:in:appropriateFor:create:) for the
preferred means of finding the correct temporary directory. For more
information about temporary files, see File System Programming Guide.
So instead, you should use FileManager.default.temporaryDirectory
or if you want an unique path:
let extractionPath = FileManager.default.temporaryDirectory.appendingPathComponent(UUID().uuidString, isDirectory: true)

Answer 3

Swift 2.1 version:
func createTempDirectory() -> String? {
let tempDirURL = NSURL(fileURLWithPath: NSTemporaryDirectory()).URLByAppendingPathComponent("XXXXXX")
do {
try NSFileManager.defaultManager().createDirectoryAtURL(tempDirURL, withIntermediateDirectories: true, attributes: nil)
} catch {
return nil
}
return tempDirURL.absoluteString
}

Answer 4

Swift 3 and up
I think a good way to do this in swift is with an extension on FileManager. This should create a unique temporary folder and return the URL to you.
extension FileManager{
func createTemporaryDirectory() throws -> URL {
let url = URL(fileURLWithPath: NSTemporaryDirectory()).appendingPathComponent(UUID().uuidString)
try createDirectory(at: url, withIntermediateDirectories: true, attributes: nil)
return url
}
}

Answer 5

Swift 3 version
func createTempDirectory() -> String? {
guard let tempDirURL = NSURL(fileURLWithPath: NSTemporaryDirectory()).appendingPathComponent("myTempFile.xxx") else {
return nil
}
do {
try FileManager.default.createDirectory(at: tempDirURL, withIntermediateDirectories: true, attributes: nil)
} catch {
return nil
}
return tempDirURL.absoluteString
}

Answer 6

A direct translation of your Objective-C code to Swift would be:
func tempDirectory()->String! {
let tempDirectoryTemplate = NSTemporaryDirectory() + "XXXXX"
var tempDirectoryTemplateCString = tempDirectoryTemplate.fileSystemRepresentation().copy()
let result : CString = reinterpretCast(mkdtemp(&tempDirectoryTemplateCString))
if !result {
return nil
}
let fm = NSFileManager.defaultManager()
let tempDirectoryPath = fm.stringWithFileSystemRepresentation(result, length: Int(strlen(result)))
return tempDirectoryPath
}
It uses the same mkdtemp() BSD method as your original code. This method creates
a directory name from the template which is guaranteed not to exist at the time where
the method is called.
Thanks to Nate Cook who figured out that reinterpretCast() can be used to treat the UnsafePointer<CChar> returned by mkdtemp() as a CString, so that it can be passed to stringWithFileSystemRepresentation(), see Working with C strings in Swift, or: How to convert UnsafePointer<CChar> to CString.
As of Xcode 6 beta 6, the reinterpretCast() is not necessary anymore and the
above code can be simplified to
func tempDirectory()->String! {
let tempDirectoryTemplate = NSTemporaryDirectory() + "XXXXX"
var tempDirectoryTemplateCString = tempDirectoryTemplate.fileSystemRepresentation()
let result = mkdtemp(&tempDirectoryTemplateCString)
if result == nil {
return nil
}
let fm = NSFileManager.defaultManager()
let tempDirectoryPath = fm.stringWithFileSystemRepresentation(result, length: Int(strlen(result)))
return tempDirectoryPath
}