Now that we have the %Folder{} struct defined, we can define its implementation for the Size protocol.
We'll first define the implementation for the %File.Stat{} struct, as we can then use this to implement the protocol for %Folder{}. Here's the implementation for %File.Stat{}:
$ cat examples/size_implementations_file_stat_and_folder.exdefimpl Size, for: File.Stat do def size(file_stat), do: file_stat.sizeend# ...
With this in place, our implementation for our %Folder{} struct is as follows:
$ cat examples/size_implementations_file_stat_and_folder.ex# ...defimpl Size, for: Folder do def size(folder) do folder.files_info |> Enum.map(&Size.size(&1)) |> Enum.sum() endend
To find out the size of a folder, ...
