[iOS 8] PhotoKit 6 – Photos Framework – モデルの変更のハンドリングとコンテンツ編集のrevert

@interface AssetViewController () <PHPhotoLibraryChangeObserver>

- (void)awakeFromNib
{
    [[PHPhotoLibrary sharedPhotoLibrary] registerChangeObserver:self];
}

- (void)dealloc
{
    [[PHPhotoLibrary sharedPhotoLibrary] unregisterChangeObserver:self];
}

#pragma mark - PHPhotoLibraryChangeObserver
 
- (void)photoLibraryDidChange:(PHChange *)changeInstance
{
    // Call might come on any background queue. Re-dispatch to the main queue to handle it.
    dispatch_async(dispatch_get_main_queue(), ^{
 
        // check if there are changes to the album we're interested on (to its metadata, not to its collection of assets)
        PHObjectChangeDetails *changeDetails = [changeInstance changeDetailsForObject:self.asset];
        if (changeDetails) {
            // it changed, we need to fetch a new one
            self.asset = [changeDetails objectAfterChanges];
        }
 
    });
}

- (void)revertImage
{
    // 編集処理がサポートされているかを問い合わせる
    // 引数にPHAssetEditOperationContentを指定
    if ([self.asset canPerformEditOperation:PHAssetEditOperationContent]) {
        // Assetの編集を実行
        [[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{
            PHAssetChangeRequest *request = [PHAssetChangeRequest changeRequestForAsset:self.asset];
            [request revertAssetContentToOriginal];
        } completionHandler:^(BOOL success, NSError *error) {
            if (!success) {
                NSLog(@"%s Error: %@", __PRETTY_FUNCTION__, error);
            }
        }];
    }
}