The specific thing you’re looking for is :erlang.fun_info:

iex(1)> f = &String.capitalize/1
&String.capitalize/1

iex(2)> :erlang.fun_info(f)
[module: String, name: :capitalize, arity: 1, env: [], type: :external]

Note that it gives a possibly-unexpected result if given a capture that uses &n forms:

iex(3)> f2 = &String.starts_with?(&1, "foo")
#Function<42.39164016/1 in :erl_eval.expr/6>
iex(4)> :erlang.fun_info(f2)
[
  pid: #PID<0.0.0>,
  module: :erl_eval,
  new_index: 42,
  new_uniq: <<74, 179, 14, 23, 76, 2, 152, 184, 122, 207, 206, 42, 63, 68, 21,
    64>>,
  index: 42,
  uniq: 39164016,
  name: :"-expr/6-fun-3-",
  arity: 1,
  env: [
    {3, %{}, {:value, &:elixir.eval_local_handler/2},
     {:value, &:elixir.eval_external_handler/3}, %{},
     [
       {:clause, 3, [{:var, 3, :_capture@1}], [],
        [
          {:call, 3,
           {:remote, 3, {:atom, 3, String}, {:atom, 3, :starts_with?}},
           [
             {:var, 3, :_capture@1},
             {:bin, 3,
              [{:bin_element, 3, {:string, 3, ~c"foo"}, :default, :default}]}
           ]}
        ]}
     ]}
  ],
  type: :local
]

Hey @stjefim, are you aware of Kernel.apply/3?

I don’t think there is a general solution as function can be anonymous. Also, storing function in a db may not be the best idea. Code will change, db record last for a long time. Also, think of the security implication.

Thank you, it will be useful after “loading function” - no need to do Functions.capture.

That’s not possible. Because you can’t turn a function value back to MFA, just like you can’t turn a value back to the variable name.

You can store the function value itself though:

binary = :erlang.term_to_binary(&MyModule.my_function/0)
# store in db
fun = :erlang.binary_to_term(binary)
fun.()

However, as I mentioned above, that’s a big foot gun.