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