Saving many photos to the camera roll.

TJLPhotoManger.m

- (void)saveImages:(NSArray *)images toGroup:(ALAssetsGroup *)group next:(void (^)(NSData *imageData))next error:(void (^)(NSError *))errorBlock completion:(void (^)())block {
    dispatch_queue_t queue = dispatch_queue_create("com.photoShare.saveToCameraRoll", NULL);

    [images enumerateObjectsUsingBlock:^(PPSAsset *obj, NSUInteger idx, BOOL *stop) {
        dispatch_async(queue, ^{
            dispatch_semaphore_t sema = dispatch_semaphore_create(0);
            [self.library writeImageDataToSavedPhotosAlbum:obj.fullImageData metadata:obj.metaData completionBlock:^(NSURL *assetURL, NSError *error) {
                if(error) {
                    errorBlock(error);
                }
                else {
                    [self.library assetForURL:assetURL resultBlock:^(ALAsset *asset) {
                        [group addAsset:asset];
                        if(next) next(obj.fullImageData);
                        dispatch_semaphore_signal(sema);

                        if(idx == images.count - 1) {
                            dispatch_async(dispatch_get_main_queue(), ^{
                                block();
                            });
                        }
                    }            failureBlock:^(NSError *error) {
                        dispatch_async(dispatch_get_main_queue(), ^{
                            errorBlock(error);
                        });
                    }];
                }
            }];
            dispatch_semaphore_wait(sema, DISPATCH_TIME_FOREVER);
        });
    }];
}