lib/project/motion-capture.rb
def save_to_assets_library(jpeg_data, &block)
    assets_library.writeImageDataToSavedPhotosAlbum(jpeg_data, metadata: nil, completionBlock: -> (asset_url, error) {
      error ? error_callback.call(error) : block.call(asset_url)
    })
  end
def save_to_assets_library(jpeg_data, &block)
    assets_library.writeImageDataToSavedPhotosAlbum(jpeg_data, metadata: nil, completionBlock: -> (asset_url, error) {
      error ? error_callback.call(error) : block.call(asset_url)
    })
  end
iOS 4-8