PiL2, ch 28.3: Adding Lua methods to an array?

[Carsten Fuchs <CarstenFuchs@...>]

Hello all,

when we have userdata with a metatable as described in the "array" 
example in the PiL1 or PiL2, chapter 28.3 "Object-Oriented Access" 
(http://www.lua.org/pil/28.3.html), I would like to be able to add more 
functions in Lua.

For example, chapter 28.3 in PiL2 starts with the example

a = array.new(1000)
print(a:size())
a:set(10, true)
print(a:get(10))

And now I'd like to be able to add a statement like

function a:OnMouseClick()
    -- do something...
    print("Hello!\n")
end


The intention here is to call a:OnMouseClick() from C/C++ code later, 
and overall it means that some "methods" of a would be 
provided/implemented by C(++) code, and others by Lua code.

When I try to do define a:OnMouseClick() as above, of course there is an 
error message saying that indexing a is not possible, because it is of 
type userdata.

==> Is there any way to be able to achieve this anyway??

I looked into the lunar.h template, but it only allows to provide 
Lua-methods on a per-class basis, e.g. with lunar, we could write

function array:OnMouseClick()
    -- Do something with "self".

    -- Note that this is a class-wide member function ("array"),
    -- not per-instance as with "a" above.
end


My currently best idea is to have the C++ code create "a" as a normal 
table, as
    a = { }
would do, then set a field with key "userdata" and value of the original 
userdata, and finally set its ("a"s) metatable to the metatable of the 
original userdata...  but I really don't know if that can work (will try 
so now), and/or if maybe there is a much better approach to this problem 
that I have overlooked.

I'd be very grateful for your help and any comments!

Best regards,
Carsten



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Carsten Fuchs    http://www.Ca3D-Engine.de/c_Carsten.php