Accessing temp directory in Swift

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 *tempDir         


        

Answer 1

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 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 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
}