Re: Question about __index and classes

[Tomas Guisasola Gorham <tomas@...>]

	Hi Michael

On Sat, 27 Aug 2011, Michael Kirsch wrote:
> There is something I don't understand about the way __index and
> metamethods work. The way I understand, the "." operator looks in the
> table itself and the ":" operator looks directly in the metatable.
	No you are wrong.  Both trigger metamethods.  The "." is syntatic
sugar for string (*) key indexing, while the ":" is syntatic sugar for
an indexing and a call using the table as the first argument.

t = {...}
t["bla"] == t.bla
t:f(arg1) == t.f(t, arg1) == t["f"](t, arg1)

> If
> so, then why is it necessary to say:
>
>    MyClass.__index = MyClass
>
> for you to be able to use ":"?
	It is not.

> If ":" looks right in the metatable, then it shouldn't be needed. To
> me it seems like what it would do is let you call metamethods using
> the "." operator, but it doesn't work that way for some reason.
	I think you are mixing things...  Sorry but I cannot follow you...

	Regards,
		Tomás

(*) My assertion is not quite correct.  The string key might be lexically
an identifier.