Table Question

local t = {}
t[1] = {text = "Engine", func = engine1}
t[2] = {text = "Engine 2", func = engine2}
t[3] = {text = "Engine 3",func = engine3}
local w,h = term.getSize()
local state = 1
function draw()
term.clear()
for i = 1,#t do
if state == i then
term.setCursorPos(((w-string.len("--> "..t[1]["text"]))/2)+1,((h/2)-1)+i)
term.write("--> "..t[i].text)
elseif state ~= i then
term.setCursorPos((((w-string.len("--> "..t[1]["text"]))/2)+1),((h/2)-1)+i)
term.write("    "..t[i].text)
end
end
end
function draw2()

end
function engine2()
rs.setOutput("back",true)
end

draw()


while true do
local event,key = os.pullEvent("key")
if key == 200 then
if state > 1 then
state = state - 1
draw()
elseif state == 1 then
state = #t
draw()
end
elseif key == 208 then
if state < #t then
state = state + 1
draw()
elseif state == #t then
state = 1
draw()
end
elseif key == 28 then
t[state]["func"]()
end
end

why does defining the table on top give me an error when I run it the first time and the second time is fine?

If I do this

local t = {}
local w,h = term.getSize()
local state = 1

function draw()
term.clear()
for i = 1,#t do
if state == i then 
term.setCursorPos(((w-string.len("--> "..t[1]["text"]))/2)+1,((h/2)-1)+i)
term.write("--> "..t[i].text)
elseif state ~= i then
term.setCursorPos((((w-string.len("--> "..t[1]["text"]))/2)+1),((h/2)-1)+i)
term.write("    "..t[i].text)
end
end
end

function draw2()


end

function engine2()
rs.setOutput("back",true)
end


draw()


t[1] = {text = "Engine", func = engine1}
t[2] = {text = "Engine 2", func = engine2}
t[3] = {text = "Engine 3",func = engine3}

while true do 
local event,key = os.pullEvent("key")
if key == 200 then
if state > 1 then
state = state - 1
draw()
elseif state == 1 then
state = #t
draw()
end
elseif key == 208 then
if state < #t then
state = state + 1
draw()
elseif state == #t then
state = 1
draw()
end
elseif key == 28 then
t[state]["func"]()
end
end

Everything work fine on this

First run:

t[2] = {text = "Engine 2", func = engine2}  -- "engine2" is currently nil, so "t[state]["func"]" is nil too.
.
.
.
function engine2()  -- "engine2" is now a function, but "t[state]["func"]" is still nil.
 ...
end
.
.
.
t[state]["func"]()  -- Attempt to call nil.

Because you didn't declare the function as local, it stays loaded in memory when the script ends. So on the second run:

t[2] = {text = "Engine 2", func = engine2}  -- t[state]["func"] now points to the "engine2" function.
.
.
.
function engine2()  -- "engine2" was already in memory, but gets redeclared here (no real effect).
 ...
end
.
.
.
t[state]["func"]()  -- Function can now be called.

In short, localise your functions, and make sure you declare them before you attempt to do anything else with them.

Bomb Bloke, on 09 December 2013 - 11:26 PM said:

First run:

t[2] = {text = "Engine 2", func = engine2}  -- "engine2" is currently nil, so "t[state]["func"]" is nil too.
.
.
.
function engine2()  -- "engine2" is now a function, but "t[state]["func"]" is still nil.
...
end
.
.
.
t[state]["func"]()  -- Attempt to call nil.

Because you didn't declare the function as local, it stays loaded in memory when the script ends. So on the second run:

t[2] = {text = "Engine 2", func = engine2}  -- t[state]["func"] now points to the "engine2" function.
.
.
.
function engine2()  -- "engine2" was already in memory, but gets redeclared here (no real effect).
...
end
.
.
.
t[state]["func"]()  -- Function can now be called.

In short, localise your functions, and make sure you declare them before you attempt to do anything else with them.

Thx So much and I accidentally click report you when I try to thanks you sorry. This is my fault.