This is a behaviour that defines how an uploader should behave. It comes in handy if you want to validate uploads or transform files before uploading.

Example

defmodule MyUploader do

  use Upload.Uploader

  def cast(file) do
    with {:ok, upload} <- Upload.cast(file) do
      extension = Upload.get_extension(upload)

      if Enum.member?(~w(.png), extension) do
        {:ok, upload}
      else
        {:error, "not a valid file extension"}
      end
    end
  end
end