keep track of already downloaded files with `alamofire` - swift

Question

how can i keep a track or record of already downloaded files in alamofire swift 2.1 so that i don t have to download the same file again ? do we have any native method for that provided by alamofire or we have to do a check before downloading any file on our directory if we already have file with that name there ???? i'm confused on how to accomplish this with a proper approach
if anybody would clear my confusion about this then it'll be so helpful for me thanks
UPDATE:
let documentsURL = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask)[0]
let fileUrl = documentsURL.URLByAppendingPathComponent(suggestedFileName)
print(fileUrl)
if !(NSFileManager.defaultManager().fileExistsAtPath(fileUrl.path!)){
self.suggestedFileName = (self.request?.response?.suggestedFilename)! // here how can i get the suggested download name before starting the download preocess ???
print("\(destination)")
request = Alamofire.download(.GET, "http://contentserver.adobe.com/store/books/GeographyofBliss_oneChapter.epub", destination: destination)
.progress { bytesRead, totalBytesRead, totalBytesExpectedToRead in
print(totalBytesRead)
// This closure is NOT called on the main queue for performance
// reasons. To update your ui, dispatch to the main queue.
dispatch_async(dispatch_get_main_queue()) {
print("Total bytes read on main queue: \(totalBytesRead)")
self.progressView.setProgress(Float(totalBytesRead) / Float(totalBytesExpectedToRead), animated: true)
}
}
.response { _, _, _, error in
if let error = error {
print("Failed with error: \(error)")
} else {
print("Downloaded file successfully")
}
}
}else {
print("file already exists")
}
in the above update am trying to get the suggestedFileName which is generated by alamofire but there's one problem when am trying to get sugestedFileName like this : suggestedFileName = (request?.response?.suggestedFilename)! in viewdidload am getting a null exception off course because there's no suggestedFileName because download not yet started so my question is that how can i get the suggestedFileName from response before starting the download ??

Answer 1

According to the docs https://github.com/Alamofire/Alamofire#downloading, you can download to a file. If your file destinations names are predictable, you could simply check to see if the contents of the file exists. For example if your are downloading data:
if let data = NSData(contentsOfURL: yourDestinationURL) {
//Do your stuff here
}
else {
//Download it
}
If you want consistency between names I suggest you avoid the Alamofire suggested destination and do this instead:
let path = NSFileManager.defaultManager().URLsForDirectory(.ApplicationSupportDirectory, inDomains: .UserDomainMask)[0] as NSURL
let newPath = path.URLByAppendingPathComponent(fileName)
Alamofire.download(.GET, "https://httpbin.org/stream/100", destination: { _ in
newPath //You have to give the destination in this closure. We could say 'return newPath' instead, they're the same thing.
})
.progress({ _ in
//progress stuff
})
.response { _, _, data, _ in
//Handle response once it's all over
}