How to move/copy an image to another album in objective-c? - ios

Question

I am writing an app which at the moment should just be able to have images in an album, dedicated to the app. The user is able to add pictures to the folder from inside the app, either by choosing an existing image or taking a new one with the camera. This functionality is however very slow, so I am wondering if I am doing it correctly.
- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
Calls this method with the chosen UIImage:
- (void)addPictureAndUpdate:(UIImage *)image{
PHFetchOptions *albumFetchOptions = [PHFetchOptions new];
albumFetchOptions.predicate = [NSPredicate predicateWithFormat:#"%K like %#", #"title", self.albumName];
PHFetchResult *album = [PHAssetCollection fetchAssetCollectionsWithType:PHAssetCollectionTypeAlbum subtype:PHAssetCollectionSubtypeAlbumRegular options:albumFetchOptions];
PHAssetCollection *assetCollection = album.firstObject;
[[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{
PHAssetChangeRequest *assetChangeRequest = [PHAssetChangeRequest creationRequestForAssetFromImage:image];
PHAssetCollectionChangeRequest *assetCollectionChangeRequest = [PHAssetCollectionChangeRequest changeRequestForAssetCollection:assetCollection];
[assetCollectionChangeRequest addAssets:#[[assetChangeRequest placeholderForCreatedAsset]]];
} completionHandler:^(BOOL success, NSError *error) {
if (!success) {
NSLog(#"Error creating asset: %#", error);
} else {
//Add PHAsset to datasource
//Update view
}
}];
This(the finishing of the ChangeRequest) is very slow, like 20-30 seconds and even more at times.
What am doing wrong? I am quite new to iOS development and obviously to the new Photos framework and I really want to learn how to do this.
Would it be smarter to seperate the two things, the showing the image and moving it? At the moment, I am storing a PHAsset for each image, which is then loaded in the requested size when needed(a thumbnail size for showing in the view and the original size when it is shown in fullscreen). Would it be smarter to always just store a UIImage, and then change the size of that? That way, I would be able to make the request to add the asset to the album, and immediatly show it as I would just add the UIImage to the datasource.
My main concerns about this are memory problems and iamge scaling problems. Would storing UIImages for an entire album be too memory heavy for an app? And, is it easy to resize a UIImage for display?
Thank you