Finding matching elements in a list or a map

When storing data in lists or maps in Elixir we can use pattern matching to access the elements of those collections easily.

Below are a few ways of how to do it.

defmodule Find do
  @moduledoc """
  Implements methods to find elements in given collections by pattern matching.
  """

  @doc """
  Finds the first element in a list to match a given pattern.
  """
  def first_match(collection) do
    Enum.find(collection, fn(element) ->
      match?({:fruit, _}, element)
    end)
  end

  @doc """
  Finds all the elements in a list that match a given pattern.
  """
  def all_matches(collection) do
    Enum.filter(collection, fn(element) ->
      match?({:fruit, _}, element)
    end)
  end
end

And then, to test the implemented methods:

iex> require Find
iex> array = [{:fruit, "Apple"}, {:vegetable, "Carrot"}, {:fruit, "Orange"}]
iex> Find.first_match(array)
{:fruit, "Apple"}
iex> Find.all_matches(array)
[{:fruit, "Apple"}, {:fruit, "Orange"}]
iex> map = %{fruit: "Apple", vegetable: "Carrot"}
iex> Find.first_match(map)
{:fruit, "Apple"}
iex> Find.all_matches(map)
[{:fruit, "Apple"}]

Additional reading: