-- enum.lua
local enum = {}
local len_key = "len"
local _ = {}
setmetatable(_, {__mode = "k"})
function enum:__len()
local i = 0
for k, v in pairs(_[self]) do
if k ~= len_key then
i = i + 1
end
end
return i
end
function enum:new(o)
local t = {}
_[t] = {[len_key] = enum.__len}
for k, v in pairs(o) do
if tonumber(k) ~= nil then
k, v = v, k - 1
end
if _[t][k] ~= nil then
error('"' .. k .. '" can not be set.', 2)
end
_[t][k] = v
end
return setmetatable(t, self)
end
function enum:__index(k)
if _[self][k] == nil then
error('"' .. k .. '" is undefined enumerator.', 2)
end
return _[self][k]
end
function enum:__newindex()
error("enum is read-only.", 2)
end
return enum
test.lua
enum = require "enum"
test = enum:new{"aa", "bb", cc = 100}
print(test.aa) --> 0
print(test.bb) --> 1
print(test.cc) --> 100
print(#test) --> 0 (Lua5.1) or 3 (Lua5.2)
print(test:len()) --> 3
--print(test.dd) --> error : "dd" is undefined enumerator.
--test.aa = 10 --> error : enum is read-only.
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