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class.lua
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class.lua
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function class(base, init)
-- a new class instance
local c = { };
if not init and type(base) == 'function' then
init = base;
base = nil;
elseif type(base) == 'table' then
-- our new class is a shallow copy of the base class!
for i ,v in pairs(base) do
c[i] = v;
end
c._base = base
end
-- the class will be the metatable for all its objects,
-- and they will look up their methods in it.
c.__index = c;
-- expose a constructor which can be called by <classname>(<args>)
local mt = { };
mt.__call = function(class_tbl, ...)
local obj = { };
setmetatable(obj, c);
if init then
init(obj, ...);
else
-- make sure that any stuff from the base class is initialized!
if base and base.init then
base.init(obj, ...);
end
end
return obj
end
c.init = init;
c.is_a = function(self, klass)
local m = getmetatable(self);
while m do
if m == klass then return true end
m = m._base;
end
return false
end
setmetatable(c, mt);
return c;
end