Save and Load Core Graphic UIImage Array on watchOS - swift

Question

I would like to be able to save a UIImage array created on the Apple Watch with watchOS and play this series of images as an animation as a group background. I can make the image array and play it but I cannot figure out how to store/save these images so I can retrieve/load them the next time I run the app so I don't have to build them every time the app runs.
Here is an example of how I am building the images with Core Graphics (Swift 3):
import WatchKit
import Foundation
class InterfaceController: WKInterfaceController
{
#IBOutlet var colourGroup: WKInterfaceGroup!
override func awake(withContext context: AnyObject?)
{
super.awake(withContext: context)
}
override func willActivate()
{
var imageArray: [UIImage] = []
for imageNumber in 1...250
{
let newImage: UIImage = drawImage(fade: CGFloat(imageNumber)/250.0)
imageArray.append(newImage)
}
let animatedImages = UIImage.animatedImage(with:imageArray, duration: 10)
colourGroup.setBackgroundImage(animatedImages)
let imageRange: NSRange = NSRange(location: 0, length: 200)
colourGroup.startAnimatingWithImages(in: imageRange, duration: 10, repeatCount: 0)
super.willActivate()
}
func drawImage(fade: CGFloat) -> UIImage
{
let boxColour: UIColor = UIColor(red: 1.0, green: 1.0, blue: 1.0, alpha: fade)
let opaque: Bool = false
let scale: CGFloat = 0.0
let bounds: CGRect = WKInterfaceDevice.current().screenBounds
let imageSize: CGSize = CGSize(width: bounds.width, height: 20.0)
UIGraphicsBeginImageContextWithOptions(imageSize, opaque, scale)
let radius: CGFloat = imageSize.height/2.0
let rect: CGRect = CGRect(x: 0.0, y: 0.0, width: imageSize.width, height: imageSize.height)
let selectorBox: UIBezierPath = UIBezierPath(roundedRect: rect, cornerRadius: radius)
let boxLineWidth: Double = 0.0
selectorBox.lineWidth = CGFloat(boxLineWidth)
boxColour.setFill()
selectorBox.fill()
// return the image
let result: UIImage = UIGraphicsGetImageFromCurrentImageContext()!
UIGraphicsEndImageContext()
return result
}
override func didDeactivate()
{
// This method is called when watch view controller is no longer visible
super.didDeactivate()
}
}
Basically I am looking for a way to save and load a [UIImage] in a manner that I can use UIImage.animatedImage(with:[UIImage], duration: TimeInterval) with the array
Is there a way to save the image array so I can load it next time I run the app rather than rebuild the images?
Thanks
Greg

Answer 1

NSKeyedArchiver and NSKeyedUnarchiver did the trick. Here is Swift code for XCode 8b4:
override func willActivate()
{
var imageArray: [UIImage] = []
let fileName: String = "TheRings"
let fileManager = FileManager.default
let url = fileManager.urls(for: .documentDirectory, in: .userDomainMask).first! as NSURL
let theURL: URL = url.appendingPathComponent(fileName)!
if let rings = NSKeyedUnarchiver.unarchiveObject(withFile: theURL.path) as? [UIImage]
{
print("retrieving rings - found rings")
imageArray = rings
}
else
{
print("retrieving rings - can't find rings, building new ones")
for imageNumber in 1...250
{
let newImage: UIImage = drawImage(fade: CGFloat(imageNumber)/250.0)
imageArray.append(newImage)
}
NSKeyedArchiver.archiveRootObject(imageArray, toFile: theURL.path)
}
let animatedImages = UIImage.animatedImage(with:imageArray, duration: 10)
colourGroup.setBackgroundImage(animatedImages)
let imageRange: NSRange = NSRange(location: 0, length: 200)
colourGroup.startAnimatingWithImages(in: imageRange, duration: 10, repeatCount: 0)
super.willActivate()
}