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

First of all, @Olshansk's answer worked like a charm for me. Thank you for that.

Next, since the initial implementation provided by @Olshansk was lacking support for list of maps, below is my code snippet extending that.

  def keys_to_atoms(string_key_map) when is_map(string_key_map) do
    for {key, val} <- string_key_map, into: %{}, do: {String.to_atom(key), keys_to_atoms(val)}
  end

  def keys_to_atoms(string_key_list) when is_list(string_key_list) do
    string_key_list
    |> Enum.map(&keys_to_atoms/1)
  end

  def keys_to_atoms(value), do: value

This the sample I used, followed by the output after passing it to the above function - keys_to_atoms(attrs)

# Input
%{
  "school" => "School of Athens",
  "students" => [
    %{
      "name" => "Plato",
      "subjects" => [%{"name" => "Politics"}, %{"name" => "Virtues"}]
    },
    %{
      "name" => "Aristotle",
      "subjects" => [%{"name" => "Virtues"}, %{"name" => "Metaphysics"}]
    }
  ]
}

# Output
%{
  school: "School of Athens",
  students: [
    %{name: "Plato", subjects: [%{name: "Politics"}, %{name: "Virtues"}]},
    %{name: "Aristotle", subjects: [%{name: "Virtues"}, %{name: "Metaphysics"}]}
  ]
}

The explanation for this is very simple. The first method is the heart of everything which is invoked for the input of the type map. The for loop destructures the attributes in key-value pairs and returns the atom representation of the key. Next, while returning the value, there are three possibilities again.

1. The value is yet another map.
2. The value is a list of maps.
3. The value is none of the above, it's primitive.

So this time, when the keys_to_atoms method is invoked while assigning value, it may invoke one of the three methods based on the type of input. The methods are organized in the snippet in a similar order.

Hope this helps. Cheers!