Error when trying to save image in NSUserDefaults using Swift
In order to save UIImage
in NSUserDefaults
, you need to convert UIImage
into NSData
using UIImageJPEGRepresentation(image, 1)
then save it in NSUserDefaults
. And on the other side, while retrieving it on another ViewController
(within that same application) you need to get NSData
and then convert it into UIImage
.
Here i am writing small code snippet in swift to demonstrate this. I tried this in XCODE 6.4
/*Code to save UIImage in NSUserDefaults on viewWillDisappear() event*/
override func viewWillDisappear(animated: Bool)
{
super.viewWillDisappear(animated)
//Get some image in image variable of type UIImage.
var image = ....
let defaults = NSUserDefaults.standardUserDefaults()
var imgData = UIImageJPEGRepresentation(image, 1)
defaults.setObject(imgData, forKey: "image")
}
/*Code to get Image and show it on imageView at viewWillAppear() event*/
override func viewWillAppear(animated: Bool)
{
super.viewWillAppear(animated)
let defaults = NSUserDefaults.standardUserDefaults()
if let imgData = defaults.objectForKey("image") as? NSData
{
if let image = UIImage(data: imgData)
{
//set image in UIImageView imgSignature
self.imgSignature.image = image
//remove cache after fetching image data
defaults.removeObjectForKey("image")
}
}
}
Updated for Swift 3:
If you want to save image in UserDefault used below lines of code save and retrieve the image;
To Save image in UserDefault:
if let image = response.result.value {
UserDefaults.standard.register(defaults: ["key":UIImageJPEGRepresentation(image, 100)!])
UserDefaults.standard.set(UIImageJPEGRepresentation(image, 100), forKey: "key")
}
To Retrieve the image from UserDefault and set it to ImageView:
var mLogoImageView = UIImageView()
if let imageData = UserDefaults.standard.value(forKey: "key") as? Data{
let imageFromData = UIImage(data: imageData)
mLogoImageView.image = imageFromData!
}
Enjoy..!
NSUserDefaults
isn't just a big truck you can throw anything you want onto. It's a series of tubes which only specific types.
What you can save to NSUserDefaults
:
NSData
NSString
NSNumber
NSDate
NSArray
NSDictionary
If you're trying to save anything else to NSUserDefaults
, you typically need to archive it to an NSData
object and store it (keeping in mind you'll have to unarchive it later when you need it back).
There are two ways to turn a UIImage
object into data. There are functions for creating a PNG representation of the image or a JPEG representation of the image.
For the PNG:
let imageData = UIImagePNGRepresentation(yourImage)
For the JPEG:
let imageData = UIImageJPEGRepresentation(yourImage, 1.0)
where the second argument is a CGFloat
representing the compression quality, with 0.0
being the lowest quality and 1.0
being the highest quality. Keep in mind that if you use JPEG, each time you compress and uncompress, if you're using anything but 1.0
, you're going to degrade the quality over time. PNG is lossless so you won't degrade the image.
To get the image back out of the data object, there's an init
method for UIImage
to do this:
let yourImage = UIImage(data:imageData)
This method will work no matter how you converted the UIImage
object to data.
In newer versions of Swift, the functions have been renamed, and reorganized, and are now invoked as:
For the PNG:
let imageData = yourImage.pngData()
For the JPEG:
let imageData = yourImage.jpegData(compressionQuality: 1.0)
Although Xcode will autocorrect the old versions for you