elixir dynamic module call

Question

How can I call function func() in a module called App.Reporting.Name

based on the string "name" which is not known until runtime

using String.to_atom or to_existing_atom does not work :

 alias App.Reporting.Name
 module = "name" |> String.capitalise |> String.to_atom     
 apply(module, :func, [])

Without the alias, this does not work either

module = "App.Reporting.Name" |> String.to_atom     
apply(module, :func, [])

I get an (UndefinedFunctionError) and (module :"App.Reporting.Name" is not available)

thanks

Dogbert · Accepted Answer · 2016-12-28 04:37:31Z

9

Your second approach is almost correct, you just need to prefix Elixir. because App.Reporting.Name is equal to :"Elixir.App.Reporting.Name", not :"App.Reporting.Name" since Elixir prefixes all module names (names starting with an uppercase letter) with Elixir. before turning it into an atom:

iex(1)> App.Reporting.Name == :"App.Reporting.Name"
false
iex(2)> App.Reporting.Name == :"Elixir.App.Reporting.Name"
true

So, this code should work:

module = "Elixir.App.Reporting.Name" |> String.to_atom     
apply(module, :func, [])

and so should this:

module = Module.concat(App.Reporting, "name" |> String.capitalize |> String.to_atom)
apply(module, :func, [])

answered Dec 28, 2016 at 4:37

Dogbert

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Comments

Harrison Lucas · Accepted Answer · 2016-12-27 22:58:09Z

1

The reason yours isn't working is because the String.to_atom does just that, turns a string into an atom. Because there is no module called "App.Reporting.Name" it's most likely App.Reporting.Name it errors.

Not sure if this is the best way to do this, just one that sprang to mind. But you could do something like this:

iex(2)> module = "Casing"
"Casing"
iex(3)> Module.concat(String, "#{module}") |> apply(:upcase, ["test sentence"])
"TEST SENTENCE"

Another solution could be to create a macro that automatically does this process, however that is not something I am that great at so you will have to go through the docs here for that one.

answered Dec 27, 2016 at 22:58

Harrison Lucas

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