Question

I tried to save NSMutableArray which contains five UIImages to NSUserDefaults and didn’t work. i got warning

-[NSUserDefaults setObject:forKey:]: Attempt to insert non-property value '(
    "UIImage: 0x4c76570,
    "UIImage: 0x4c76570",
    "UIImage: 0x4c76570",
    "UIImage: 0x4c76570",
    "UIImage: 0x4c76570"
)' of class '__NSArrayM'.

OK seems like i need to archive my Array into NSData. But how do i make UIImage to conform NSCoding? Should i transform my images to NSData first or maybe there is an easier way?

Answer 1

Yes, you’ll need to either use the UIImagePNGRepresentation or UIImageJPEGRepresentation functions to retrieve the image’s binary data in the desired format, which you can then serialize into an NSArray.

An example:

UIImage *someImage = ...;
NSData *someImageData = UIImagePNGRepresentation(someImage);
[yourArray addObject:someImageData];

//...

[[NSUserDefaults standardUserDefaults] setObject:yourArray forKey:@"images"];