After talking about it so much with my fellow apprentices, I finally got my first taste of elixir and the Phoenix framework today while pairing at a client.My initial impressions of the language are extremely positive, because it is dynamic it looks a lot like Ruby, but because it is functional it is was pretty easy to reason about and follow.

The pattern matching elixir provides is definitely one of the langauge’s hallmarks and through my work today I was able to see some of it’s versatility and power. Take the following example:

Bypass.expect bypass, fn
  %Plug.Conn{request_path: "/home"} = conn ->
    assert something = something_else
  %Plug.Conn{request_path: "/users"} = conn ->
    assert this = that

The Bypass library is a light-weight, quick way to create a custom “plug” (Plug is the clojure Ring of the elixir world) in place of an actual HTTP server. It’sessentially a mock HTTP server without actually being a mock (apparently it’s somewhat frowned upon to use mocks in elixir). Anyway, all we are doing in the code above is passing in a Bypass struct and an anonymous function that contains some assertions about the response we are expectiing from our fake Bypass server

In elixir, Anonymous functions take the following form:

  parameter_list -> function_body
  parameter_list -> function_body

Thanks to pattern matching, the function can take multiple parameter lists to

provide alternate function bodies, which is exactly exactly what is happening inthe Bypass example above. There’s still something strang though. The = sign is part of the pattern? Yeah, atually. We are basically saying, “if the parameter map we pass in has a request_path of “/home” then assign it to the variable conn, and execute the assertions in the function body. Pretty sweet!

There are still quite a bit of nuance in pattern matching that I have yet to understand, but what I see and understand so far has made me very excited about elixir. I look forward to playing around with it some more.