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["nil"] 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["nil"] = 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