Today I Learned

hashrocket A Hashrocket project

Invoke Elixir Functions with Apply

I had a weird problem yesterday: I wanted to pass a function into another function and then invoke it, all for the sake of a friendly API.

Elixir's apply to the rescue. Here's the rough implementation.

defmodule Example do
  def do_things(index, rotation, operator) do
    apply(Kernel, operator, [index, rotation])

iex> Example.do_things(10, 20, :+)
iex> Example.do_things(10, 20, :-)

apply also accepts your own functions:

defmodule Example do
  def do_things(index) do
    apply(__MODULE__, :make_bigger, [index])

  def make_bigger(a) do
    a * 10000

iex> Example.do_things(100)

The module name (Example) will work in place of __MODULE__, if you prefer. This seems like a pretty powerful feature.

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