Re: from: Lua Module Function Critiqued
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- Subject: Re: from: Lua Module Function Critiqued
- From: steve donovan <steve.j.donovan@...>
- Date: 2013年10月10日 08:08:35 +0200
On Wed, Oct 9, 2013 at 8:14 PM, Andrew Starks <andrew.starks@trms.com> wrote:
> If this approach doesn't contain surprises that I'm not seeing, then I
> believe that it is equivalent to the intent of `module`, and thus I
> can safely ignore the on-coming debate about module. :)
Pretty much so!
Penlight has a useful pattern for modules, which you actually
suggested and implemented ;)
-- mod.lua
local print = print
local _ENV, M = require 'pl.import_into' ()
print(_ENV,M)
function answer ()
-- all the Penlight modules are available in this environment!
return pretty.write(utils.split '10 20 30', '')
end
return M
-- testmod.lua
local mod = require 'mod'
print(mod.utils, mod.answer)
$ lua52 testmod.lua
table: 000000000051CD80 table: 000000000051CD80
table: 0000000000554A10 function: 0000000000568230
Hello, the module is leaking, it has a reference to utils! To get a
'shadow table', pass true to the function returned by
'pl.import_into':
table: 000000000078CF60 table: 000000000078CD80
nil function: 000000000078F4D0
The module no longer leaks, because the _environment_ of the module is
not the same as the module itself; the module is a 'shadow table' that
gets only the exported functions.
This pattern could be generalized for non-PL applications, obviously.