Re: OOP and modules

[Tomas <tomas@...>]

	Hi David

> module ("clip.parsetree")
>
> function _M:new(name, transitionRecord)
>   assert( self == _M, format("You need to call %s:new(), not %s.new()!", 
> _NAME, _NAME )  )
>
>   -- normal stuff follows as above...
> end
	You could omit the _M (but then you'll have to write the implicit
`self'):

function new (self, name, transitionRecord)
...

> This seems to work, and I can now do:
> require ("clip.parsetree")
> parsetree = clip.parsetree:new()
>
> which is what I wanted.
>
> Is this the "right" way of implementing classes in modules? Is there a better 
> way? Is there something wrong with this approach that I should be aware of?
	I think there is nothing wrong with your implementation.
	I would like to add that if you want some inheritance, you could
use the second argument of `module()' to achieve an elegant solution.
Let's define a basic object class:

local setmetatable = setmetatable
module"obj"
function inherit (self)
    return function (newclass)
        setmetatable (newclass, self)
        self.__index = self
        return newclass
    end
end
function new (self, o)
    o = o or {}
    setmetatable (o, self)
    self.__index = self
    return o
end

	Now you can define a new class which extends the previous `obj':

local obj = require"obj"
module ("myobj", obj:inherit())

	Class `myobj' will "inherit" the methods `new' and `inherit'
from class `obj'.
		Tomas