ExperimentalGear/scripts/common/class.lua

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2022-05-06 00:05:20 +02:00
---Member lookup helper function
---@param key string
---@param bases any
---@return any
local function search(key, bases)
for _, base in ipairs(bases) do
local v = base[key] -- try `i'-th superclass
if v then return v end
end
end
---Create polimorphic class
---@generic BaseT, T
---@param cls T # class metatable
---@param o? table # initial parameters
---@param ... BaseT # base class metatables (if any)
---@return T # class instance
function CreateInstance(cls, o, ...)
o = o or {}
local nargs = select("#", ...)
local vargs = { select(1, ...) }
cls.__index = cls
if nargs == 1 then
-- single inheritance
local base = vargs[1]
setmetatable(cls, {__index = base})
o = base.new(o)
elseif nargs > 1 then
-- multiple inheritance (note: slow(er) member lookup)
setmetatable(cls, {__index = function(t, k) return search(k, vargs) end})
for _, base in ipairs(vargs) do
o = base.new(o)
end
end
setmetatable(o, cls)
return o
end