Re: Environment behavior
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- Subject: Re: Environment behavior
- From: Philipp Janda <siffiejoe@...>
- Date: 2013年12月07日 17:12:25 +0100
Am 07.12.2013 16:49 schröbte Peter Cawley:
The inner _ENV is an upvalue of func and subItem.func, and crucially
is a shared upvalue: the first upvalue of func is inner _ENV, and the
first upvalue of subItem.func is inner _ENV.
... and you can confirm that `item.func`, `item.subItem.func`, and
`component` share the same upvalue by
print( debug.upvalueid( item.func, 1 ) )
print( debug.upvalueid( item.subItem.func, 1 ) )
print( debug.upvalueid( component, 1 ) )
As such,
debug.setupvalue(item.func, 1, x) and
debug.setupvalue(item.subItem.func, 1, x) have the same effect.
If you want to change the upvalue reference of one function without
affecting the others you can use `debug.upvaluejoin`:
debug.setupvalue( item.func, 1, env1 )
local function dummy() return env2 end
debug.upvaluejoin( item.subItem.func, 1, dummy, 1 )
-- now env2 in dummy and _ENV in subItem.func refer to the same upvalue
print( debug.upvalueid( dummy, 1 ) )
print( debug.upvalueid( item.subItem.func, 1 ) )
-- an now those two functions use different _ENVs:
item.func()
item.subItem.func()
Philipp
On Sat, Dec 7, 2013 at 3:39 PM, Bruno Deligny <bruno.deligny@gmail.com> wrote:
Hi
I was playing with environements and i dont understand this behavior.
local env1 = {print=print, a=1}
local env2 = {print=print, a=2}
local component = load([[
item = {
func = function()
print(a)
end,
subItem = {
func = function()
print(a)
end,
}
}
]])
component()
debug.setupvalue(item.func, 1, env1)
debug.setupvalue(item.subItem.func, 1, env2)
item.func()
item.subItem.func()
This print:
2
2
I was hoping it printed:
1
2
It would be great if someone could explain to me how env is propagated.
Thanks