You shouldn't save large data inside core data, an Apple engineer told me this little trick at the last WWDC:
You can use the property "Allows external storage":
By doing this as far as i know, your image will be stored somewhere in the file system, and inside core data will be saved a link to your picture in the file system. every time you'll ask for the picture, core data will automatically retrive the image from the file system.
To save the image as NSData you can do:
let image = UIImage(named: "YourImage")
let imageData = NSData(data: UIImageJPEGRepresentation(image, 1.0))
managedObject?.setValue(imageData, forKey: "YourKey")
Remember that 1.0 in the UIImageJPEGRepresentatio means that your using the best quality and so the image will be large and heavy:
The quality of the resulting JPEG image, expressed as a value from 0.0
to 1.0. The value 0.0 represents the maximum compression (or lowest
quality) while the value 1.0 represents the least compression (or best
quality).
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