Control Flow

The case statement

defmodule Account do
    def list_transactions(filename) do
        {result, content} = File.read(filename)

        if result == :ok do
            "Content: #{content}"
        else
            if result == :error do
                "Error: #{content}"
            end
        end
    end
end

defmodule Account do
    def list_transactions(filename) do
        {result, content} = File.read(filename)
        case result do
            :ok -> "Content: #{content}"
            :error -> "Error: #{content}"
        end
    end
end

The pattern matching can be over tuples.

defmodule Account do
    def list_transactions(filename) do
        case File.read(filename) do
            {:ok, content} -> "Content: #{content}"
            {:error, type } -> "Error: #{type}"
        end
    end
end

Using case with Guard Clauses

defmodule Account do
    def list_transactions(filename) do
        case File.read(filename) do
        {:ok, content}
            when byte_size(content) > 10 -> "Content: (...)"
        {:ok, content} -> "Content: #{content}"
        {:error, type} -> "Error: #{type}"
    end
end