Lua inheritance - oop

Question

I have two classes in Lua.
test1 = {test1Data = 123, id= {0,3}}
function test1:hello()
print 'HELLO!'
end
function test1:new (inp)
inp = inp or {}
setmetatable(inp, self)
self.__index = self
return inp
end
test2 = {}
function test2:bye ()
print 'BYE!'
end
function test2:create_inst( baseClass )
local new_class = {}
local class_mt = { __index = new_class }
function new_class:create()
local newinst = {}
setmetatable( newinst, class_mt )
return newinst
end
if baseClass then
setmetatable( new_class, { __index = baseClass } )
end
return new_class
end
a = test1:new({passData='abc'})
print (a.test1Data, a.passData, a:hello())
c = test2:create_inst(a)
print (c.test1Data, c.passData,c:hello(), c:bye())
I want to inherit test2 from test but leave in the specified test2 methods bye.
Everything works except for bye:method.
How can I solve this problem?

Answer 1

You return an empty table in test2:create_inst(), at no point does anything reference test2, so the function test2:bye() is not in the table returned by test2:create_inst()

Answer 2

In your code, test2 actually has nothing to do with the table you are instancing, this new_class table you return from test2:create_inst is the new instance. So naturally it has no field named bye. Simple modification:
function test2:create_inst( baseClass )
...
if baseClass then
setmetatable( new_class, { __index = baseClass } )
end
...
function new_class:bye()
print("bye!")
end
return new_class
end

Answer 3

I think the answer want to implement Multi-Inheritance that new_class inherit "test2" and "baseClass".
local function search(k, objlist)
local i = 0
local v
while objlist[i] then
v = objlist[i][k]
if v then return v end
end
end
function class(...)
local parents = (...)
local object = {}
function object:new(o)
o = o or {}
setmetatable(o, object)
return o
end
object.__index = object
setmetatable(object,
{__index=function(t, k)
search(k, parents)
end})
return object
end
c = class(a, test2)
print(c.test1Data, c.passData,c:hello(), c:bye())