How does composition work?

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#1

I’m planning to make AI that can basically do anything the player can do the only obvious difference is it’s not controlled by a player instead I’m going to use a behavior tree and I wanna use composition to do this neatly.

My current plan is going to be to make 3 classes (module scripts) a character class that will set up everything they have in common methods, states, health, walk speed, etc. Then a player class will probably just handle input, and then the AI class which will control the behavior tree.

The issue though is I don’t think this is how composition works so what would be the proper way to go about doing this?

Edit: if I’m understanding this correctly essentially what I need to do is isolate the needed behavior into its own class and then add then I can just add that behavior to any class that needs it?

#2

yes you are doing it right, you just stick stuff inside other stuff and redo the functions on the outside if needed. I like to use ._Inner to reference the main component.

local Entity = {}
-- ...
function Entity:Attack(dmg: number) end
-- ...

local Player = {}
Player.__index = Player
function Player.new(hp: number)
    local self = setmetatable({}, Player)
    self._Inner = Entity.new(hp)
    return self
end

function Player:Attack()
    self._Inner:Attack(1337)
end

local Zombie = {}
-- same as above

function Zombie:Attack()
    self._Inner:Attack(888)
end