How to convert map keys from strings to atoms in Elixir

Question

What is the way to convert %{\"foo\" => \"bar\"} to %{foo: \"bar\"} in Elixir?

Answer 1

I really liked Roman Bedichevskii's answer ... but I needed something that will thoroughly atomize the keys of deeply nested yaml files. This is what I came up with:

   @doc """
   Safe version, will only atomize to an existing key
   """
   def atomize_keys(map) when is_map(map), do: Map.new(map, &atomize_keys/1)
   def atomize_keys(list) when is_list(list), do: Enum.map(list, &atomize_keys/1)
   def atomize_keys({key, val}) when is_binary(key),
     do: atomize_keys({String.to_existing_atom(key), val})
   def atomize_keys({key, val}), do: {key, atomize_keys(val)}
   def atomize_keys(term), do: term

   @doc """
   Unsafe version, will atomize all string keys
   """
   def unsafe_atomize_keys(map) when is_map(map), do: Map.new(map, &unsafe_atomize_keys/1)
   def unsafe_atomize_keys(list) when is_list(list), do: Enum.map(list, &unsafe_atomize_keys/1)
   def unsafe_atomize_keys({key, val}) when is_binary(key),
     do: unsafe_atomize_keys({String.to_atom(key), val})
   def unsafe_atomize_keys({key, val}), do: {key, unsafe_atomize_keys(val)}
   def unsafe_atomize_keys(term), do: term

It's main limitation is that if you feed it a tuple {key, value} and the key is a binary, it will atomize it. That is something you want for keyword lists, but it is probably someone's edge case. In any case, YAML and JSON files don't have a concept of a tuple, so for processing those, it won't matter.