LÖVE

Code: Select all

local function _null_() end

local function goto(self, state, ...)
    if self.state then (self.state._leave or _null_)(self, ...) end
    self.state = state and self.states[state] or {}
    return (self.state._enter or _null_)(self, ...)
end

local function stateful_index(class)
    return function(self, key)
        local st = rawget(self, 'state') or {}
        return (st[key] or class[key])
    end
end

local function add_state(class, name, methods)
    assert(class.states, "Class is not stateful")
    class.states[name] = methods
    return class
end

local function make_stateful(class, methods)
    class.states = {}
    class.__index = stateful_index(class)
    class.goto = goto
    class.add_state = add_state
    return class
end

return make_stateful

Code: Select all

make_stateful = require 'stateful'

local Enemy = class('Enemy')
make_stateful(Enemy)

function Enemy:initialize(health) self.health = health end
function Enemy:speak() print('My health is ' .. tostring(self.health)) end
Enemy:add_state('Immortal', {
    _enter = function() print('I became Immortal!') end,
    speak = function() print('I am UNBREAKABLE!!') end,
    die = function() print('I can not die now!') end,
    _leave = function() print('The gods have forsaken me') end,
})
-- alternatives:
--    local Immortal = {}
--    function Immortal:speak() (...) end
--    (...)
--    Enemy:add_state('Immortal', Immortal)
-- or:
--    Enemy.states.Immortal = { ... }
-- or even (you get the idea):
--    Enemy.states.Immortal = Immortal

local peter = Enemy:new(10)

peter:speak() --> My health is 10
peter:goto('Immortal') --> I became Immortal~
peter:speak() --> I am UNBREAKABLE!!
peter:die() --> I can not die now!
peter:goto(nil) --> The gods have forsaken me
peter:speak() -- My health is 10