error handling in Swift 2

i have to fix the follow code for swift2.

if !UIImagePNGRepresentation(img).writeToFile(imagePath, options: nil, error: &error) {
                        if let actualError = error {
                            NSLog("Image not saved. \(actualError)")
                        }
                    }

To compile it i have this error on if row: Cannot invoke writeToFile with an argument list of type (String, options: _, error: inout NSError?)

How I can fix it.

Try it with

UIImagePNGRepresentation(img)?.writeToFile(imagePath, atomically: true)

instead. Check the Apple Docs.

Edit:

To answer your question more precisely use the error handling in Swift 2.

do {
    try UIImagePNGRepresentation(img)?.writeToFile(imagePath, options: .DataWritingAtomic)
} catch let error as NSError {
    print("Image not saved. \(error.description)")
}