CODEWITHSUNDEEP
erlangelixir
Charles Okwuagwu
Charles Okwuagwu

Reputation: 10876

Is there an equivalent to __MODULE__ for named functions in Elixir/ Erlang?

Is there an equivalent for retrieving the name of a function just like like __MODULE__ retrieves the name of a Module in Elixir/Erlang?

Example: 

defmodule Demo do
  def home_menu do
    module_name = __MODULE__
    func_name = :home_menu 
    # is there a __FUNCTION__
  end
End

EDITED

The selected answer works,

but calling the returned function name with apply/3 yields this error:

[error] %UndefinedFunctionError{arity: 4, exports: nil, function: :public_home, module: Demo, reason: nil}

I have a function :

defp public_home(u, m, msg, reset) do

end

The function in question will strictly be called within its module.

Is there a way to dynamically call a private function by name within its own module?

Upvotes: 18

Views: 5426

Answers (4)

T0plomj3r
T0plomj3r

Reputation: 695

__ENV__.function |> elem(0)

Will result with the name of the function you are currently in.

Upvotes: 1

theartofrain
theartofrain

Reputation: 1837

To add to Aleksei's answer, here is an example of a macro, f_name(), that returns just the name of the function.

So if you use it inside a function, like this:

def my_very_important_function() do
   Logger.info("#{f_name()}: about to do important things")
   Logger.info("#{f_name()}: important things, all done")
end

you will get a log statement similar to this:

my_very_important_function: about to do important things
my_very_important_function: important things, all done

Details:

Here is the definition of the macro:

defmodule Helper do
  defmacro f_name() do
    elem(__CALLER__.function, 0)
  end
end

(__CALLER__ is just like __ENV__, but it's the environment of the caller.)

And here is how the macro can be used in a module:

defmodule ImportantCodes do
  require Logger
  import Helper, only: [f_name: 0]

  def my_very_important_function() do
     Logger.info("#{f_name()}: doing very important things here")
  end
end

Upvotes: 3

Stratus3D
Stratus3D

Reputation: 4906

Yes, there is. In Erlang there are several predefined macros that should be able to provide the information you need:

% The name of the current function
?FUNCTION_NAME

% The arity of the current function (remember name alone isn't enough to identify a function in Erlang/Elixir)
?FUNCTION_ARITY 

% The file name of the current module
?FILE 

% The line number of the current line
?LINE

Source: http://erlang.org/doc/reference_manual/macros.html#id85926

Upvotes: 4

Aleksei Matiushkin
Aleksei Matiushkin

Reputation: 120990

▶ defmodule M, do: def m, do: __ENV__.function  
▶ M.m                                                 
#⇒ {:m, 0}

Essentially, __ENV__ structure contains everything you might need.

Upvotes: 31

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