递增录制的音频文件名

Question

Xcode 7.3.1, Swift 2

I have the following line of code in my view controller that sets the file name of my recorded audio. Although each file has a unique name, I would really like it to be shorter, but unique. I would like to increment the file name by one if it already exists.

I am not sure the proper terminology to properly look this up, so I am hoping one of you could point me in the right direction.

// Set the default audio file
    let audioFileURL = directoryURL.URLByAppendingPathComponent("PWAC_" + NSUUID().UUIDString + ".m4a")

Answer 1

A repeat loop will do:

var index = 0
var audioFileURL: NSURL!

repeat {
    index += 1
    audioFileURL = directoryURL.URLByAppendingPathComponent("PWAC_\(index).m4a")
} while NSFileManager.defaultManager().fileExistsAtPath(audioFileURL.path!)

Answer 2

You can use NSDefault to keep running id. It stored permanently in your app even though the apps is terminated.

For example here, I use a class with static function:

class FileUtil {

    let key = "runningId" 

    static func getRunningID() {
        let prefs = NSUserDefaults.standardUserDefaults()
        // set initial value if first time

        if var runningid = prefs.valueForKey(key) as? Int{
           print("current id: \(runningid)")
           // increase by 1 and return
           runningid += 1
           // dont forget to save back after increment
           prefs.setInteger(runningid, forKey: key)

           return runningid;
        }else{         
           // not set yet, then set the init value
           prefs.setInteger(1, forKey: key)          
        }
    }
}

So in your controller could simply call

 let audioFileURL = directoryURL.URLByAppendingPathComponent("PWAC_" + FileUtil. getRunningID() + ".m4a")

Answer 3

Each your Audio file has a unique name with date string everytime.

let date = NSDate()

let dateFormatter = NSDateFormatter()
dateFormatter.dateStyle = .MediumStyle
dateFormatter.dateFormat = "yyyy-MM-ddHHmmssSSS"
let string = dateFormatter.stringFromDate(date)

audioFileURL = directoryURL.URLByAppendingPathComponent("PWAC_\(string).m4a")