cocoalumberjack log to one file

I am developing mac application in that application I need to log to folder, where already some other application is also logging,so need to create only one file in that folder, when file rolling occurs the whole contents in that log folder are deleting .this code I am using .I don't want delete contents in log folder and is it possible to use only file with constant name .Please help me.

// Configure CocoaLumberjack
        DDLog.addLogger(DDASLLogger.sharedInstance())
        DDLog.addLogger(DDTTYLogger.sharedInstance())
        // Initialize File Logger
        let manager : BaseLogFileManager = BaseLogFileManager(logsDirectory:K.LogFileDir)
        let fileLogger: DDFileLogger = DDFileLogger(logFileManager: manager) // File Logger

        fileLogger.maximumFileSize = 1024*1024*20
        fileLogger.doNotReuseLogFiles = false
        fileLogger.logFileManager.maximumNumberOfLogFiles = 1
        DDLog.addLogger(fileLogger)

class BaseLogFileManager : DDLogFileManagerDefault
{
    override var newLogFileName: String! { get {
        return K.LogFileName
        }}
    override func isLogFile(fileName: String!) -> Bool
    {
        return true
    }
}

Work around is to disable rolling frequency, don't assign maximum size or rollingFrequency and check size using NSFileManager. If file size is greater than specific limit, remove and create new file.

       // Configure CocoaLumberjack
        DDLog.addLogger(DDASLLogger.sharedInstance())
        DDLog.addLogger(DDTTYLogger.sharedInstance())
        // Initialize File Logger
        let manager : BaseLogFileManager = BaseLogFileManager(logsDirectory:K.LogFileDir)
        let fileLogger: DDFileLogger = DDFileLogger(logFileManager: manager) // File Logger
        do {
                let attr : NSDictionary? = try NSFileManager.defaultManager().attributesOfItemAtPath(K.LogFileDir+"/"+K.LogFileName)
                if let _attr = attr {
                    if _attr.fileSize() > 1024*1024*10
                    {
                        NSFileManager.defaultManager().createFileAtPath(K.LogFileDir+"/"+K.LogFileName, contents: NSData(), attributes: nil)
                    }
                }
            } catch {
                print("Error: \(error)")
            }
        fileLogger.doNotReuseLogFiles = false
        fileLogger.logFileManager.maximumNumberOfLogFiles = 1
        DDLog.addLogger(fileLogger)