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-- Class.lua
-- Compatible with Lua 5.1 (not 5.0).
--
-- Modified to use a metatable to reference base objects instead
-- or performing shallow copies. This means smaller classes that
-- are a bit more dynamic at the expence of some performance.
_G.class = function( base )
if ( base ~= nil ) then
local baseType = type( base );
if ( baseType ~= 'table' ) then
error( "Base class is not a table. Base class was a " .. baseType );
end
end
-- The class definition table. Contains all of the actual class
-- methods, constructor, and an IsA function automatically
-- provided.
local c = { };
c.base = base;
c.IsA = function( self, klass )
local m = getmetatable( self );
while m do
if m == klass then
return true;
end
m = m.base;
end
return false;
end
-- The class definition metatable. This is used to hook up
-- base classes and then to register a call handler that is
-- used to construct new instances of the class.
local mt = { };
mt.__index = base;
mt.__call = function( class_tbl, ... )
if ( class_tbl.Abstract ) then
error "Abstract class cannot be constructed.";
end
-- Create the new class instance.
local instance = { };
setmetatable( instance, { __index = c } );
-- Invoke the constructor if it exists.
if ( ( instance.Constructor ~= nil ) and ( type( instance.Constructor ) == 'function' ) ) then
instance:Constructor( ... );
end
return instance;
end
setmetatable( c, mt );
return c;
end
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