云风的个人空间 : Lua 函数重载[LuaFunctionOverload]

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[InterWiki]在 lua 中实现函数的重载

local function create()
	local arg_table = {}
	local function dispatcher (...)
		local tbl = arg_table
		local n = select ("#",...)
		local last_match
		for i = 1,n do
			local t = type(select(i,...))
			local n = tbl[t]
			last_match = tbl["..."] or last_match
			if not n then
				return last_match (...)
			end
			tbl = n
		end
		return (tbl["__end"] or tbl["..."])(...)
	end
	local function register(desc,func)
		local tbl = arg_table
		for _,v in ipairs(desc) do
			if v=="..." then
				assert(not tbl["..."])
				tbl["..."] = func
				return
			end
 
			local n = tbl[v]
			if not n then
				n = {}
				tbl[v]=n
			end
			tbl = n
		end
		tbl["__end"] = func
	end
	return dispatcher, register, arg_table
end
 
local all={}
 
local function register(env,desc,name)
	local func = desc[#desc]
	assert(type(func)=="function")
	desc[#desc] = nil
 
	local func_table
	if all[env] then
		func_table = all[env]
	else
		func_table = {}
		all[env] = func_table
	end
 
	if env[name] then
		assert(func_table[name])
	else
		env[name],func_table[name] = create()
	end
 
	func_table[name](desc,func)
end
 
define = setmetatable({},{
	__index = function (t,k)
		local function reg (desc)
			register(getfenv(2),desc,k)
		end
		t[k] = reg
		return reg
	end
})


下面试一下:

define.test {
	"number",
	function(n)
		print("number",n)
	end
}
 
define.test {
	"string",
	"number",
	function(s,n)
		print("string number",s,n)
	end
}
 
define.test {
	"number",
	"...",
	function(n,...)
		print("number ...",n,...)
	end
}
 
define.test {
	"...",
	function(...)
		print("default",...)
	end
}
 
test(1)
test("hello",2)
test("hello","world")
test(1,"hello")


输出:

number  1
string number   hello   2
default hello   world
number ...      1       hello
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