为啥 TIC-80 让我尝试索引零值错误？
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【中文标题】为啥 TIC-80 让我尝试索引零值错误？【英文标题】：Why is TIC-80 giving me the attempt to index a nil value error?为什么 TIC-80 让我尝试索引零值错误？ 【发布时间】：2022-01-19 23:18:13 【问题描述】：因此，我正在 itch.io 上为 Game Jam 开发一款游戏，我正在使用这款名为 TIC-80 的非常简洁的 Fantasy 控制台，可在 tic80.com 上找到。我的问题是，虽然我了解错误消息是什么以及它的含义，但我不明白为什么它会给我这个错误。
错误消息（在 TIC-80 控制台中）：
>[string "-- title: The Clone
Wars..."]:144: attempt to index a nil
value (field '?')
stack traceback:
[string "-- title: The Clone
Wars..."]:144: in function 'TIC'
有问题的代码：
-- title: The Clone Wars
-- author: DinoNuggies
-- desc: Help the jedi destroy the clones!
-- script: lua
--Functions
function sign(n) return n>0 and 1 or n<0 and -1 or 0 end
function lerp(a,b,t) return (1-t)*a + t*b end
function tablelength(T)
local count = 0
for _ in pairs(T) do count = count + 1 end
return count
end
--End of Functions
--Variables
player =
spr = 256,
sprMod = 0,
x = 1,
y = 1,
vx = 0,
vy = 0,
dirX = 0,
dirY = 0,
flip = 0,
shoot = false,
gun =
t = 0,
spr = 258,
sprMod = 0,
x = 0,
y = 0,
modX = 0,
modY = 0,
flip = 0,
rot = 0,
tile =
r0 = 0,
r1 = 0,
l0 = 0,
l1 = 0,
u0 = 0,
u1 = 0,
d0 = 0,
d1 = 0,
m = 0,
m =
x = 0,
y = 0,
left = false,
right = false,
middle = false,
cam =
activate = true,
x = 120,
y = 64,
--Bullet Class & Functions
bulletMod = 0
bullet =
function bullet:new()
local this =
spr = 260,
x = player.x,
y = player.y,
vx = 0,
vy = 0,
mx = m.x - (player.x + cam.x),
my = m.y - (player.y + cam.y),
t = 0,
return this
end
function bullet:remove()
local this =
spr = nil,
x = nil,
y = nil,
vx = nil,
vy = nil,
mx = nil,
my = nil,
t = nil,
return this
end
--End of Variables
function TIC()
cls()
--Camera
if cam.activate then
cam.x = math.min(120, lerp(cam.x, 120-player.x, 0.05))
cam.y = math.min(64, lerp(cam.y, 64-player.y, 0.05))
ccx = cam.x / 8 + (cam.x % 8 == 0 and 1 or 0)
ccy = cam.y / 8 + (cam.y % 8 == 0 and 1 or 0)
end
map(15 - ccx, 8 - ccy, 31, 18, (cam.x % 8) - 8, (cam.y % 8) - 8, 0)
--End of Camera
--Gun Physics
m.x, m.y, m.left, m.middle, m.right = mouse()
gun.x = player.x + cam.x
gun.y = player.y + cam.y
bullets = tablelength(bullet) - 2
flick = (time() // 16) % 16 == 0
if m.left then m.leftp = flick else m.leftp = false end
--Gun Display
if m.x > player.x + cam.x + 4 then
gun.flip = 0
gun.modX = 4
else
gun.flip = 1
gun.modX = -4
end
--Gun Firing
if m.leftp == true then
bullet[bullets] = bullet:new()
if m.x > player.x + cam.x + 4 then
bullet[bullets].vx = 8
else
bullet[bullets].vx = -8
end
end
--End of Gun Physics
--Bullet Physics
if bullets > 0 then
for i=0,bullets-1 do
bullet[i].x = bullet[i].x + bullet[i].vx --LINE 144, THE ONE IN QUESTION
bullet[i].y = bullet[i].y + bullet[i].vy
spr(bullet[i].spr, bullet[i].x + cam.x, bullet[i].y + cam.y, 0, 1)
bullet[i].t = bullet[i].t + 1
if bullet[i].t > 16 then
bullet[i] = bullet:remove()
bullet[i] = nil
end
end
end
bullets = tablelength(bullet) - 2
--End of Bullet Physics
--Drawing
--Sprites
spr(player.spr + player.sprMod, player.x + cam.x, player.y + cam.y, 0, 1, player.flip)
spr(gun.spr + gun.sprMod, gun.x + gun.modX, gun.y + gun.modY, 0, 1, gun.flip, gun.rot)
--Debug
print("Debug:", 1, 1, 11)
print("X: " .. (player.x // 8) + 15 .. " Y: " .. (player.y // 8) + 9, 1, 8, 11)
print("BLTs: " .. bullets .. " ", 1, 16, 11)
--End of Drawing
--Player Movement
player.x = player.x + player.vx
player.y = player.y + player.vy
if key(1) and player.x > -120 then
player.vx = -1
player.sprMod = 1
player.dirX = 0
elseif key(4) then
player.vx = 1
player.sprMod = 0
player.dirX = 1
else
player.vx = 0
end
if key(23) and player.y > -64 then
player.vy = -1
player.dirY = 0
elseif key(19) then
player.vy = 1
player.dirY = 1
else
player.vy = 0
end
if btnp(0) then player.y = player.y - 1
elseif btnp(1) then player.y = player.y + 1
elseif btnp(2) then player.x = player.x - 1
elseif btnp(3) then player.x = player.x + 1
end
--End of Movement
--Player Collision
tile.r0 = mget(((player.x + 7) // 8) + 15, ((player.y - 9) // 8) + 9)
tile.r1 = mget(((player.x + 7) // 8) + 15, ((player.y - 2) // 8) + 9)
tile.l0 = mget(((player.x - 2) // 8) + 15, ((player.y - 9) // 8) + 9)
tile.l1 = mget(((player.x - 2) // 8) + 15, ((player.y - 2) // 8) + 9)
tile.u0 = mget(((player.x - 1) // 8) + 15, ((player.y - 10) // 8) + 9)
tile.u1 = mget(((player.x + 6) // 8) + 15, ((player.y - 10) // 8) + 9)
tile.d0 = mget(((player.x - 1) // 8) + 15, ((player.y - 1) // 8) + 9)
tile.d1 = mget(((player.x + 6) // 8) + 15, ((player.y - 1) // 8) + 9)
if player.dirX == 1 then
if fget(tile.r0, 0) or fget(tile.r1, 0) then
player.vx = 0
end
elseif player.dirX == 0 then
if fget(tile.l0, 0) or fget(tile.l1, 0) then
player.vx = 0
end
end
if player.dirY == 0 then
if fget(tile.u0, 0) or fget(tile.u1, 0) then
player.vy = 0
end
elseif player.dirY == 1 then
if fget(tile.d0, 0) or fget(tile.d1, 0) then
player.vy = 0
end
end
--End of Player Collision
--Misc
if keyp(3) then
if cam.activate then
cam.activate = false
else
cam.activate = true
end
end
--End of Misc
end
--DON'T WORRY ABOUT ANYTHING PAST THIS POINT, IT'S ONLY SPRITE AND TILE DEFINITIONS FOR TIC-80 VISUALS
-- <TILES>
-- 000:6666666666666666666666666666666666666666666666666666666666666666
-- 001:6666666666566566666666656666666665665666666665666566666666666666
-- 002:6668666666898566666866656666666665665866686689868986686668666666
-- 003:6656556666555556555556555555556555555555665555556556555666655566
-- 016:dddddddeddddddefddeeeeffddeeeeffddeeeeffddeeeeffdeffffffefffffff
-- 017:6226622661266126222222221121112161266126612661265126512665266525
-- 018:6228622661298126222222221121112161266126612681268126512668266525
-- 019:6226522661255126222222221121112151255125612551255126512665255525
-- </TILES>
-- <SPRITES>
-- 000:00cccc000cccccd00cbbbbb0ccbbcbbdcccfefcd0dddddd000ceec0000c00c00
-- 001:00cccc000cccccd00bbbbbd0cbbcbbcdccfefccd0dddddd000ceec0000c00c00
-- 002:000000000000000000000000000eeeed000efff0000ef0000000000000000000
-- 003:0000ed00000eef0000eef0000eef000000eef000000ee0000000000000000000
-- 004:0000000000000000000000000aaaaaa00aaaaaa0000000000000000000000000
-- </SPRITES>
-- <MAP>
-- 000:010101010101010101010101010101010101010101010101010101010101010000000000000000000000101010000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001
-- 001:010000000000000000000000000000101000101000001000000010101001010000000000100000000000101010000000000000000000100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001
-- 002:010001000100010000000000000010000000100010001000100010001001010000000010100000000000101010000000000000001010100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001
-- 003:010001000100000000000000000000101000100010001000100010100001010000000010000000000000101000000000000000001000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001
-- 004:010001010100010000000000000000001000100010001000100010000001010000000010000000000000101010000000000000000000001000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001
-- 005:010001000100010000000000000010100000001010000010100010000001010000000010000000000000101010000000000000000000101000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001
-- 006:010000000000000000000000000101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001
-- 007:010000000000000000000000000101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001
-- 008:010000000000000000000000000101301010000000000000000000000000000000000000101010000000101000000000000000000010101000000001000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001
-- 009:010000000000000000000000000101101010100000000000000000000000000000001010101000000000101000000000000000000000000000000001000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001
-- 010:010000000000000000000000000101101010000000000001111101000000001111111121211111110000101000000000000000000000000000000001000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001
-- 011:010000000000000000000000000101000000000000001000000001000000000000001020101000000000101000000000000000000000000000000001000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001
-- 012:010000000000000000000000000101000000000000011111111101010001010000101010000000000010101000000000000000000000000000000001000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001
-- 013:010000000000000000000000000101000000000010101000000001011101010000101000000000000010100000000000000000000000000000000001000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001
-- 014:010000000000000000000000000101000000000010101010000000000000010000000000000000000010100000000000000000000000000000000001000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001
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-- 016:010101010101010101010101010101000000000000000000000000000000010000000000000000001010000000000000001010000000000000000001000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001
-- 017:010101010101010101010101010101000000000000000000000000000000000000000000000000101010000000000010102000000000000000000001000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001
-- 018:000000000000000000000000000101000000000000000000000010100000000000000000000000101000000000001010000000000000000000000001000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
-- 019:000000000000000000001010000101000000000000000000000000100000000000000000000010101000001111211110000000001010000000000001000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
-- 020:000000001000000000001000000101000000000000000000000000101000000000000000001010101000000010101011111100000000000000000001000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
-- 021:000000000000000000001010100101101010000000000000000000000000000000000000101000000000001010200000000011110000000000000001000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
-- 022:000000000000000000000000000101001010100000000000000000000000000000000010101000000010101010100000000000001111000000000001000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
-- 023:000000000000000000000000000101000000000000000000000000000000000000001010100000000010101010000000000000000000110000000001000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
-- 024:000000000000000000000000000101000000000000000000000000000000000000001010100000001020201000000000000000100000001100102001000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
-- 025:000000000000000000000000000101000000000000000000000000000000000000101010000000001020100000000000000000100000000011212101000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
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-- 033:000000000000000000000000000101010101010101010101010101010101010101010101010101010101010101010101010101010101010101010101000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
-- 135:010101010101010101010101010101010101010101010101010101010101010000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001
-- </MAP>
-- <WAVES>
-- 000:00000000ffffffff00000000ffffffff
-- 001:0123456789abcdeffedcba9876543210
-- 002:0123456789abcdef0123456789abcdef
-- </WAVES>
-- <SFX>
-- 000:020002000200020002000200020002000200020002000200020002000200020002000200020002000200020002000200020002000200020002000200304000000000
-- 001:020002000200020002000200020002000200020002000200020002000200020002000200020002000200020002000200020002000200020002000200307000000000
-- 002:02000200020002000200020002000200020002000200020002000200020002000200020002000200020002000200020002000200020002000200020030b000000000
-- </SFX>
-- <FLAGS>
-- 000:00000000000000000000000000000000101010100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
-- </FLAGS>
-- <PALETTE>
-- 000:1a1c2c5d2810814428ca9581ffcd7575ae442495482571793c55c22c9dfae20000000000f4f4f494b0c2566c86333c57
-- </PALETTE>
触发错误的原因是玩家发射第二颗子弹之后。发射一颗子弹后，子弹在队列中被创建、显示和消失，但在第二颗子弹开始存在后，它停止并给我错误。我已经改变了很多东西，似乎每次我引用其中一个项目符号对象值时存在多个时，它都会向我发送错误，这是我不明白的，因为我认为我已经用for 循环解决了这个问题。
因此，如果您立即发现任何看起来不太正确的东西，请告诉我，如果您对 TIC-80 或 API 的作用一无所知，我相信 TIC-80网站可以比我解释得更好。
如果您想运行游戏、查看实际问题并弄乱代码，请从网站下载 TIC-80 并运行此文件： https://drive.google.com/file/d/18ti0NboNNN9Yog6l_n73usF_eX_86EN4/view?usp=sharing
【问题讨论】：
一些bullet[i] 在第 144 行是 nil。您可以通过在第 #156 行之前插入代码来“压缩”bullet 数组（将 nil 移到末尾）来修复它
【参考方案1】：
让我们看看你的子弹处理能力
第一次致电TIC：
bullets 为 0。我们在 bullet[0] 中添加一个项目符号
第二次通话：
bullets 是 1。我们在bullet[1] 中添加了一个项目符号。
现在，作为bullets > 0，我们输入子弹物理 if 语句。
我们对该项目符号进行一些计算并增加bullet[0].t
下面的调用我们做同样的事情。我们添加一个项目符号并处理除新项目符号之外的所有项目，就像我们上面所做的那样。
当子弹的 t 字段变为 > 16 时，我们将其从 bullet 中删除。
首先我们删除最旧的子弹bullet[0]。但在接下来的调用中，我们再次从i = 0 开始循环。所以bullet[i] 是nil，因此在bullet[i].x 中对其进行索引会导致观察到的错误。
旁注：
这毫无意义。
function bullet:remove()
local this =
spr = nil,
x = nil,
y = nil,
vx = nil,
vy = nil,
mx = nil,
my = nil,
t = nil,
return this
end
所有 nil 值的表只是一个空表。所以只需返回一个空表。
除此之外，您不需要该功能，因为它没有任何用处。
bullet[i] = bullet:remove()
bullet[i] = nil
第一行是不必要的。您不必先分配一个空表，然后再分配 nil。只需分配nil。
如果您只是将项目符号保留在表格的数组部分中，您就不需要自己的 tablelength 函数，然后减去 2 btw。 然后，您还可以使用 table.remove 删除项目符号，而不会在项目符号列表中产生意外的空白。
【讨论】：
谢谢，我终于明白了，for 循环总是从 0 开始，而 bullet[0] 并不总是存在，即使 bullet[1] 存在。 TYSM！ Game Jam 将在 2 天内到期，祝我好运！
我有一个问题，有没有办法可以将表格向左移动？示例：bullet[0] 和 bullet[1] 存在，很快 bullet[0] 被删除，然后将所有内容从 bullet[1] 移动到新的空 bullet[0] 和理论上 bullet[2] 到 bullet[1] 如果存在，你知道吗我是说？
不要从 0 开始你的表，而是从 1 开始。然后你可以使用 table.remove 来实现这一点以上是关于为啥 TIC-80 让我尝试索引零值错误？的主要内容，如果未能解决你的问题，请参考以下文章