Functional programming patterns IN elixir As opposed to Object Oriented design

Program maintenance is an entropy-increasing process, and even its most skilful execution only delays the subsistence of the system into unfixable obsolescence

– Fred Brooks

what if we build Minecraft in elixir?

There have been quite a few FP vs OO threads lately, I would consider reading through and contributing to one of those instead of starting a new one. Topics tagged functional-programming

What if we build elixir in minecraft?

thats awesome.

imagine meme
get this man a shield
you didnt have to cut me off meme
brain exploding meme.

ps: I cant post meme, I will get banned

For this specific example of Person then I would look into Protocol. It focuses on what functionality you need from the data structures you have.

I’ve always been a bit puzzled by teaching OOO as you have a base class of Animal and then have it inheriting from that. Because it’s the wrong lessons often and makes people over engineer their designs.

Classes are about how you store things in memory and you use inheritance to be able to access internal structures.

Elixir is very nice for a flow processing where you have a structure and are modifying in each step, eg:
JSON |> Struct |> Email message |> Send Email

With Elixir and other functional languages you know can know exactly where a problem originated while with Classes you are sort of scratching you head and wondering how did this variable get messed up.

For something like vending machines it’s just a state machine and I feel like it fits better than Classes.

Ducktyping can work well in functional programming. E.g. take elixirs datetime handling. You can do DateTime.utc_now() |> Time.to_iso8601() and it will work, because the fields Time.to_iso8601 expects are a simple subset of the fields %DateTime{} holds. No need for any inheritance.

Some essential rules:

1. Let data be data.
2. Use CRC (Create, Reduce, Convert) pipelines. Most things in elixir and FP is essentially reducing over some state.
3. Use modules to organise related functions that operate on some state.
4. If you wish to compose use import or delegate to other functions in other modules.
5. If you want polymorphic behaviour use protocols
6. If you want to derive functional behaviour with your own overrides use behaviors

Look at the Enum module, it can work on data elements of any type, so think in terms of steps or an algorithm and really let the data be just data.

For true OO semantics look at Elixir process modules such as genservers or liveviews which are objects as per the Alan Kay definition, they accept messages as the only means of interacting with them and manage private state in their own process context.