Lua Metatables Make tables callable
Example
There is a metamethod called __call, which defines the bevahiour of the object upon being used as a function, e.g. object(). This can be used to create function objects:
-- create the metatable with a __call metamethod
local meta = {
__call = function(self)
self.i = self.i + 1
end,
-- to view the results
__tostring = function(self)
return tostring(self.i)
end
}
function new_counter(start)
local self = { i = start }
setmetatable(self, meta)
return self
end
-- create a counter
local c = new_counter(1)
print(c) --> 1
-- call -> count up
c()
print(c) --> 2
The metamethod is called with the corresponding object, all remaining arguments are passed to the function after that:
local meta = {
__call = function(self, ...)
print(self.prepend, ...)
end
}
local self = { prepend = "printer:" }
setmetatable(self, meta)
self("foo", "bar", "baz")
