Replace Image when if image present in gallery ios - ios

Question

In this code we used "alamofire" for download the image but present there i want to replace the image so please help me. When i get response then image present then i have get error code 516 (Already Image existing) so please help me after get response.
i want replace the old image or delete old image.
func setUI() {
self.btnCancel.layer.borderWidth = 1.0
self.btnCancel.layer.cornerRadius = 3.0
self.btnCancel.addShadowView()
print("-------------------------------- method Call")
if let url = NSURL(string: strFileName) {
print(url)
let destination = Alamofire.Request.suggestedDownloadDestination(directory: .DocumentDirectory, domain: .UserDomainMask)
self.request = Alamofire.download(.GET, url, parameters: nil, encoding: ParameterEncoding.URL,destination:destination)
.progress { bytesRead, totalBytesRead, totalBytesExpectedToRead in
dispatch_async(dispatch_get_main_queue()) {
print("Total bytes read on main queue: \(totalBytesRead)")
print("Progress on main queue: \(Float(totalBytesRead) / Float(totalBytesExpectedToRead))")
print("totalBytesExpectedToRead",totalBytesExpectedToRead)
self.CountPercentage.text! = String(format: "%.f%%",self.viewProgressBar.progress * 100)
self.viewProgressBar.progress = (Float(totalBytesRead) / Float(totalBytesExpectedToRead))
}
}
.response { request, response, _, error in
print("\(request?.URL)") // original URL request
print(error)
if !(error == nil) {
if !(error!.code != NSURLErrorCancelled) {
print("cancel----------")
} else if (error!.code == 516) {
print("fileURL: \(destination(NSURL(string: "")!, response!))")
let filePath = destination(NSURL(string: "")!, response!)
self.alertAction("File downloaded successfully.", filePath: filePath)
} else {
CommonMethods.sharedInstance.showAlertWithMessage((error?.localizedDescription)!, withController: self)
}
} else {
print("fileURL: \(destination(NSURL(string: "")!, response!))")
let filePath = destination(NSURL(string: "")!, response!)
self.alertAction("File downloaded successfully.", filePath: filePath)
}
}
}
}