Module:require when needed
- The following documentation is located at Module:require when needed/documentation. [edit]
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A helper function which can be used in place of require if it's not certain that the module in question will be needed. If the module has already been loaded, then it is simply returned; if it hasn't, then it won't be loaded until it is first used.
This is generally useful when defining variables at the start of a module.
local getmetatable = getmetatable local ipairs = ipairs local loaded = package.loaded local pairs = pairs local require = require local select = select local setmetatable = setmetatable local tostring = tostring local unpack = unpack or table.unpack -- Lua 5.2 compatibility local function get_nested(obj, ...) local n = select("#", ...) if n == 0 then return obj end obj = obj[...] for i = 2, n do obj = obj[select(i, ...)] end return obj end local function get_obj(mt) local obj = require(mt[1]) if #mt > 1 then obj = get_nested(obj, unpack(mt, 2)) end mt[0] = obj return obj end local function __call(self, ...) local mt = getmetatable(self) local obj = mt[0] if obj == nil then obj = get_obj(mt) end return obj(...) end local function __index(self, k) local mt = getmetatable(self) local obj = mt[0] if obj == nil then obj = get_obj(mt) end return obj[k] end local function __ipairs(self) local mt = getmetatable(self) local obj = mt[0] if obj == nil then obj = get_obj(mt) end return ipairs(obj) end local function __newindex(self, k, v) local mt = getmetatable(self) local obj = mt[0] if obj == nil then obj = get_obj(mt) end obj[k] = v end local function __pairs(self) local mt = getmetatable(self) local obj = mt[0] if obj == nil then obj = get_obj(mt) end return pairs(obj) end local function __tostring(self) local mt = getmetatable(self) local obj = mt[0] if obj == nil then obj = get_obj(mt) end return tostring(obj) end return function(modname, ...) local mod = loaded[modname] if mod ~= nil then return get_nested(mod, ...) end return setmetatable({}, { modname, __call = __call, __index = __index, __ipairs = __ipairs, __newindex = __newindex, __pairs = __pairs, __tostring = __tostring, -- TODO: other metamethods, if needed. ... }) end