iOS realizes the function of having pictures locally and then getting pictures from locally

//Save the image locally+ (void)SaveImageToLocal:(UIImage*)image Keys:(NSString*)key {
 NSUserDefaults* preferences = [NSUserDefaults standardUserDefaults];
 //[preferences persistentDomainForName:LocalPath];
 [preferences setObject:UIImagePNGRepresentation(image) forKey:key];
}
 
//Is there any relevant pictures locally+ (BOOL)LocalHaveImage:(NSString*)key {
 NSUserDefaults* preferences = [NSUserDefaults standardUserDefaults];
 //[preferences persistentDomainForName:LocalPath];
 NSData* imageData = [preferences objectForKey:key];
 if (imageData) {
  return YES;
 }
 return NO;
}
 
//Get pictures from local+ (UIImage*)GetImageFromLocal:(NSString*)key {
 NSUserDefaults* preferences = [NSUserDefaults standardUserDefaults];
 //[preferences persistentDomainForName:LocalPath];
 NSData* imageData = [preferences objectForKey:key];
 UIImage* image;
 if (imageData) {
  image = [UIImage imageWithData:imageData];
 }
 else {
  NSLog(@"Not obtained pictures from local");
 }
 return image;
}