The simplest way to accomplish what you’ve written is to look up replacement keys in a supplied map. For instance:

defmodule KeyRenamer do
  @key_replacements %{
    "First Name [Required]" => "first_name",
    "Last Name [Required]" => "last_name",
    "Email Address [Required]" => "email"
  }

  def rename_keys(map) do
    Map.new(map, fn k, v ->
      new_key = Map.get(@key_replacements, k, k)
      {new_key, v}
    end
  end
end

An alternative approach would be to fix the code that’s generating these keys - for instance, if it’s extracting a value from an HTML label maybe it should be using the input's name or something instead…

I don’t mind being that guy that comments on OLD threads. I ran into a sexy way to rename some keys (or all if you want). I tried googling for it later and couldn’t find it. Google just keep sending me back to this thread. I eventually found the solution in some old code. So, I’m going to dump this solution here so next time I’ll find it faster. (and maybe it will help someone else)

To rename SOME of the keys:

bad_data = %{
  "lat" => 12.43244,
  long: -5.342,
  name: "something",
  age: 91
}

good_data = Map.new(bad_data, fn
  {"lat", lat} -> {"latitude", lat}
  {:long, long} -> {:longitude, long}
  anything -> anything
end)

Results:

%{
:age => 91,
:longitude => -5.342,
:name => "something",
"latitude" => 12.43244
}

I mixed :keys and “keys” in the example to show it works with both.

good_data should now have the keys latitude, longitude, name, age. It might be cool if Hexdoc had a section showing some common uses that aren’t functions, but indexed like functions. Example “rename_key()” Don’t need the function because you can easily do it like (copy and paste example above)

If the keys are known and static, and you don’t need to make this logic reusable, you could also use plain pattern-matching:

  def rename_keys(%{
    "First Name [Required]" => first_name,
    "Last Name [Required]" => last_name,
    "Email Address [Required]" => email
  }) do
    %{first_name: first_name, last_name: last_name, email: email}
  end

You might remove [Required] with String.replace + trim. You might even transform “LastName” to “last_name” with Macro.underscore.

But how do You want him to translate “Email Address” to “email”?

Unless You use some custom rules…

for "Last Name [Required]" → "last_name"

key |> String.trim(" [Required]") |> String.downcase() |> String.replace(" ", "_")

for "Email Address [Required]" → "email", you might just pattern match on the special case in a multiple function clause

defp rename_key({"Email Address [Required]", val}), do: {"email", val}
defp rename_key({key, val}) do
  # operate on the key
  {new_key, val}
end