You could also have multiple function heads for this.

defmodule Foo do
  def bar(%{"file" => file}) do
    # Do something if the "file" key is found
  end
  def bar(attrs) do
    # Do something if none of the previous function heads match
  end
end

Keep in mind you can have more than two function heads.

Previous two replies are what I would usually reach for.

That being said, you can also do this:

map1 = %{file: "what.ever"}
map2 = %{name: "myself", age: 177}
match? %{file: _}, map1  # this yields true
match? %{file: _}, map2, # this yields false

However, this would mean you will use if / else in your code which is something I actively avoid ever since I learned functional programming. Using case is a very slight (if any) improvement over it but nowadays I’d go for @Ankhers’s approach, every time.

Glad we could help.

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