Swift - Write Image from URL to Local File - json

Question

I've been learning swift rather quickly, and I'm trying to develop an OS X application that downloads images.
I've been able to parse the JSON I'm looking for into an array of URLs as follows:
func didReceiveAPIResults(results: NSArray) {
println(results)
for link in results {
let stringLink = link as String
//Check to make sure that the string is actually pointing to a file
if stringLink.lowercaseString.rangeOfString(".jpg") != nil {2
//Convert string to url
var imgURL: NSURL = NSURL(string: stringLink)!
//Download an NSData representation of the image from URL
var request: NSURLRequest = NSURLRequest(URL: imgURL)
var urlConnection: NSURLConnection = NSURLConnection(request: request, delegate: self)!
//Make request to download URL
NSURLConnection.sendAsynchronousRequest(request, queue: NSOperationQueue.mainQueue(), completionHandler: { (response: NSURLResponse!, data: NSData!, error: NSError!) -> Void in
if !(error? != nil) {
//set image to requested resource
var image = NSImage(data: data)
} else {
//If request fails...
println("error: \(error.localizedDescription)")
}
})
}
}
}
So at this point I have my images defined as "image", but what I'm failing to grasp here is how to save these files to my local directory.
Any help on this matter would be greatly appreciated!
Thanks,
tvick47

Answer 1

In Swift 3:
Write
do {
let documentsURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
let fileURL = documentsURL.appendingPathComponent("\(fileName).png")
if let pngImageData = UIImagePNGRepresentation(image) {
try pngImageData.write(to: fileURL, options: .atomic)
}
} catch { }
Read
let documentsURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
let filePath = documentsURL.appendingPathComponent("\(fileName).png").path
if FileManager.default.fileExists(atPath: filePath) {
return UIImage(contentsOfFile: filePath)
}

Answer 2

The following code would write a UIImage in the Application Documents directory under the filename 'filename.jpg'
var image = .... // However you create/get a UIImage
let documentsPath = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)[0] as String
let destinationPath = documentsPath.stringByAppendingPathComponent("filename.jpg")
UIImageJPEGRepresentation(image,1.0).writeToFile(destinationPath, atomically: true)

Answer 3

In swift 2.0, stringByAppendingPathComponent is unavailable, so the answer changes a bit. Here is what I've done to write a UIImage out to disk.
documentsURL = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask).first!
if let image = UIImage(data: someNSDataRepresentingAnImage) {
let fileURL = documentsURL.URLByAppendingPathComponent(fileName+".png")
if let pngImageData = UIImagePNGRepresentation(image) {
pngImageData.writeToURL(fileURL, atomically: false)
}
}

Answer 4

UIImagePNGRepresentaton() function had been deprecated. try image.pngData()

Answer 5

#IBAction func savePhoto(_ sender: Any) {
let imageData = UIImagePNGRepresentation(myImg.image!)
let compresedImage = UIImage(data: imageData!)
UIImageWriteToSavedPhotosAlbum(compresedImage!, nil, nil, nil)
let alert = UIAlertController(title: "Saved", message: "Your image has been saved", preferredStyle: .alert)
let okAction = UIAlertAction(title: "Ok", style: .default)
alert.addAction(okAction)
self.present(alert, animated: true)
}
}

Answer 6

Update for swift 5
just change filename.png to something else
func writeImageToDocs(image:UIImage){
let documentsPath = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0] as String
let destinationPath = URL(fileURLWithPath: documentsPath).appendingPathComponent("filename.png")
debugPrint("destination path is",destinationPath)
do {
try image.pngData()?.write(to: destinationPath)
} catch {
debugPrint("writing file error", error)
}
}
func readImageFromDocs()->UIImage?{
let documentsPath = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0] as String
let filePath = URL(fileURLWithPath: documentsPath).appendingPathComponent("filename.png").path
if FileManager.default.fileExists(atPath: filePath) {
return UIImage(contentsOfFile: filePath)
} else {
return nil
}
}