PICO-8 Class-like Objects in pico-8 https://www.lexaloffle.com/bbs/?tid=2951

.md

With the introduction of the function type() it is now possible to know the type of the variable.

So I tried to find a way to implement a simple class system and I think I found a way

First we need a function to copy tables

function copy(o)
  local c
  if type(o) == 'table' then
    c = {}
    for k, v in pairs(o) do
      c[k] = copy(v)
    end
  else
    c = o
  end
  return c
end

Then we can declare our objects the following way:

vec = {}
vec.x = 0
vec.y = 0
function vec:add(v)
  self.x += v.x
  self.y += v.y
end
function vec:subs(v)
  self.x -= v.x
  self.y -= v.y
end
function vec:mult(c)
  self.x *= c
  self.y *= c
end

To create multiple instances of vector, we just need to copy the object and edit it's attributes

a = copy(vec)
b = copy(vec)
a.x = 1
a.y = 2
b.x = 3
b.y = -1

And when we call the a:add(b) we get a.x == 4, a.y == 1

What's more we can define "subclass"

vec3 = copy(vec)
vec3.z = 0
function vec3:printz()
  print(self.z)
end

The function printz() will run just fine on copies of vec3 but will return an error on copies of vec