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Can't figure out how to access fluidbox
Posted: Wed May 17, 2017 6:22 pm
by yay
Hi!
I can't figure out what I'm doing wrong...
I checked that I have the right entity reference by destroying it and watching it disappear in-game. Also double-checked that a fluid icon is actually visible the output slot of the building GUI.
Code: Select all
for i=1,#entity.fluidbox do
local fluidbox = entity.fluidbox[i]
if not fluidbox == nil then
print("Emptying " .. fluidbox["type"] .. "( " .. fluidbox["amount"] .. ")")
entity.damage(fluidbox["amount"], "player")
entity.fluidbox[i] = nil
else
print(i .. "nil")
end
end
(I called it on_tick.)
Output:
TTY wrote:...
1nil
2nil
1nil
2nil
...
Whyyyyyyyyy!?!?
-__-
Re: Can't figure out how to access fluidbox
Posted: Wed May 17, 2017 8:08 pm
by yay
I took a look at "Bottleneck", which accesses the fluidboxed (thanks!) and changed:
Code: Select all
if not fluidbox == nil[code]
to
[code]if fluidbox
And with that it works - I don't understand why.
Is that a LUA thing or is that something to do with the operator in the factorio API?
Re: Can't figure out how to access fluidbox
Posted: Wed May 17, 2017 8:37 pm
by prg
Re: Can't figure out how to access fluidbox
Posted: Wed May 17, 2017 11:50 pm
by Nexela
Code: Select all
fluidbox = nil
if not fluidbox == nil then
evaluates to
which evalautes to
And since it is false goes to the else part
Re: Can't figure out how to access fluidbox
Posted: Thu May 18, 2017 6:22 pm
by prg
Nexela wrote:Code: Select all
fluidbox = nil
if not fluidbox == nil then
evaluates to
which evalautes to
And since it is false goes to the else part
That's not what happens.
According to
operator precedence, "not" has higher priority than "==".
So in this expression
"not fluidbox" gets evaluated first. Depending on the fluidbox variable, this will become true (if it's nil) or false (if it contains an actual fluidbox table).
Now both "true == nil" and "false == nil" are false, so we always go into the else branch.
Re: Can't figure out how to access fluidbox
Posted: Thu May 18, 2017 9:51 pm
by yay
AAAAARGH, thanks, now I see it!
My brain reads LUA as Python - I looked at that line a hundred times, never would have found the problem xD
Re: Can't figure out how to access fluidbox
Posted: Thu May 18, 2017 10:46 pm
by Nexela
Could be worse I totally missed the order of not before ==
Thanks prg