so im gettin this error so i know theres something i probably gotta fix here but i have no idea how .thanks
SCRIPT ERROR: #gcphone/server/server.lua:205: attempt to index a nil value (local 'items')
CODE FROM LINE 205
ESX.RegisterServerCallback('crew-phone:phone-check', function(source, cb)
local xPlayer = ESX.GetPlayerFromId(source)
if not xPlayer then return; end
for k, v in pairs(Config.Phones) do
local items = xPlayer.getInventoryItem(v)
if items.count > 0 then
cb(v)
return
end
end
cb(nil)
end)
ESX.RegisterServerCallback('crew-phone:item-check', function(source, cb, data)
local xPlayer = ESX.GetPlayerFromId(source)
if not xPlayer then return; end
local items = xPlayer.getInventoryItem(data)
cb(items.count)
end)
This error tells you that items is a nil value and Lua complains about it because you try to index it as in items.count. That doesn't make sense if items is nil
It's like referring to a book page of a non-existant book.
local items is nil because xPlayer.getInventoryItem(data) returned nil
Check wether the local script provides a string for data when triggering the server event and if xPlayer actually has an item like that.
Also check your RegisterServerCallback. The function you define there is the callback. Why is there another callback in that function argument? I think you're confusing things and probably should refer to the manual again.
https://esx-framework.github.io/es_extended/server/functions/registerservercallback/
so when i try to buy something in shop it's just drop me this error.How to fix this?
Code:
RegisterServerEvent('esx_shops:buyItem')
AddEventHandler('esx_shops:buyItem', function(itemName, amount, zone)
local _source = source
local xPlayer = ESX.GetPlayerFromId(_source)
local sourceItem = xPlayer.getInventoryItem(itemName)
amount = ESX.Round(amount)
-- is the player trying to exploit?
if amount < 0 then
print('esx_shops: ' .. xPlayer.identifier .. ' attempted to exploit the shop!')
return
end
Error:
SCRIPT ERROR: #esx_supermarket/server/main.lua:68: attempt to index a nil value (local 'xPlayer')
xPlayer is a nil value. nil values may not be indexed. Doing so causes an error.
So anything like xPlayer[something], xPlayer.something or xPlayer:something() is not allowed.
In your first example
local xPlayer = ESX.GetPlayerFromId(_source)
local sourceItem = xPlayer.getInventoryItem(itemName)
xPlayer is nil because ESX.GetPlayerFromId(_source) did not return a player. Most likely because _source is nil. At least there is nothing in your code that would indicate that source is not nil.
Befor you try to index possible nil values, check wether they are nil.
Please read the Lua manual and do a beginners tutorial.
I'm using this (old) Lua module to save and access tables from local files (if there is a better way, please shout I'm not invested) -- https://github.com/gideros/table.save/blob/master/table.save-0.94.lua
It's been working great, but now I'm trying to save key value pairs I'm getting the error:
attempt to call global exportstring (a nil value)
I'm new to Lua. The error is on line 108 on that file I linked to. Any ideas?
I've tried creating blank tables, or basic tables without key value pairs, this works fine. It's when I come to insert strings the issues arise.
This will work:
local myTable = {}
myTable[0] = 2
inputOutputTable.save(myTable, "testytesty")
local testy = inputOutputTable.load("testytesty")
print("Testing 123... " .. testy[0])
However this wont:
local myTable = {}
myTable["welcome"] = "1"
I get : attempt to call global 'exportstring' (a nil value)
Expected results - it saves the table.
What happens - it throws the error.
So I have a table using Lua and within it is a variable, but I can't figure out how to reach it because of its name. I was able to use json.prettify( _id ) in order to view whats in the table. All I want is the id within this table but because of how it's named I can't seem to get what's inside of _id, I tried both
_id[1] but that == nil
_id.$oid but that gave me a runtime error
printed response: _id = {
"$oid":"597015b757203b04d6941d45"
}
interesting note is that #_id == 0
Use
tableName[ 'variableName' ]
or
tableName.variableName
Note: Sometimes you can not use both form for example:
tableName[ 'name with spaces' ] -- ok
tableNames.name with spaces -- error
I think operator # can not be used with non-indexed tables.
You need decode json string to Lua table and get value in any way:
local json = require("json")
local str = [[ { "$oid":"597015b757203b04d6941d45" } ]]
local t_res= json.decode(str)
-- access
print( t_res["$oid"] )
-- or
local k,v = next(t_res)
print( v )
-- or
for k, v in pairs(t_res) do
print(v)
break
end
PS: Lua operator # only for a regular array, with non-nil values.
In order to overcome the fact that the name of the variable included the '$' symbol the correct way to get the variable within the table was to use:
_id['$oid'], this worked.
_id.$oid gave a runtime error.
When call a lua function like
PrintMe(MyVariableName)
I would like to be able to actually print "MyVariableName" and not it's value(well, for demo purposes).
Obviously I could just pass the string but that requires extra quotes and I also would like to print it's value.
e.g.,
MyVariable = 4
PrintVariable(MyVariable)
Would print "MyVariable is 4" or whatever
I do not want to have to duplicate the name and variable like
PrintVariable(MyVariable, "MyVariable")
as this is unnecessary duplication.
Can lua handle it?
What I'm doing now is passing the variable name in quotes and using loadstring to get the value but I would like to just pass the variable directly without the extra unnecessary quotes(which I thought debug.getlocal did but it ends up returning the value instead of the name).
Here is mock example
function printme1(var, val)
print(var.." = "..val)
end
function printme2(v)
local r
loadstring("r = "..v)() -- equivalent to r = a but must be used since v is a string representing a and not the object a
print(v.." = "..tostring(r))
end
function printme3(v)
-- unknown
end
a = 3
printme1("a", a)
printme2("a")
printme3(a)
In this case all 3 should print the same thing. printme3 obviously is the most convenient.
You can't say PrintVariable(MyVariable), because Lua gives you no way of determining which variable (if any; a constant could have been used) was used to pass an argument to your function. However, you can say PrintVariable('MyVariable') then used the debug API to look for a local variable in the caller's scope which has that name:
function PrintVariable(name)
-- default to showing the global with that name, if any
local value = _G[name]
-- see if we can find a local in the caller's scope with that name
for i=1,math.huge do
local localname, localvalue = debug.getlocal(2,i,1)
if not localname then
break -- no more locals to check
elseif localname == name then
value = localvalue
end
end
if value then
print(string.format("%s = %s", name, tostring(value)))
else
print(string.format("No variable named '%s' found.", name))
end
end
Now you can say:
PrintVariable('MyVariable')
While in this case will print "MyVariable = 4".
Not, if you really want to do this without the quotes, you could check the caller's locals for variables that have a supplied value, but that's occasionally going to give you the wrong variable name if there is more than one variable in the caller's scope with a given value. With that said, here's how you'd do that:
function PrintVariable(value)
local name
-- see if we can find a local in the caller's scope with the given value
for i=1,math.huge do
local localname, localvalue = debug.getlocal(2,i,1)
if not localname then
break
elseif localvalue == value then
name = localname
end
end
-- if we couldn't find a local, check globals
if not name then
for globalname, globalvalue in pairs(_G) do
if globalvalue == value then
name = globalname
end
end
end
if name then
print(string.format("%s = %s", name, tostring(value)))
else
print(string.format("No variable found for the value '%s'.", tostring(value)))
end
end
Now you can say PrintVariable(MyVariable), but if there happened to be another variable in the caller's scope with the value 4, and it occurred before MyVariable, it's that variable name that will be printed.
you can do stuff like this with the debug library... something like this does what you seem to be looking for:
function a_func(arg1, asdf)
-- if this function doesn't use an argument... it shows up as (*temporary) in
-- calls to debug.getlocal() because they aren't used...
if arg1 == "10" then end
if asdf == 99 then end
-- does stuff with arg1 and asdf?
end
-- just a function to dump variables in a user-readable format
function myUnpack(tbl)
if type(tbl) ~= "table" then
return ""
end
local ret = ""
for k,v in pairs(tbl) do
if tostring(v) ~= "" then
ret = ret.. tostring(k).. "=".. tostring(v).. ", "
end
end
return string.gsub(ret, ", $", "")
end
function hook()
-- passing 2 to to debug.getinfo means 'give me info on the function that spawned
-- this call to this function'. level 1 is the C function that called the hook.
local info = debug.getinfo(2)
if info ~= nil and info.what == "Lua" then
local i, variables = 1, {""}
-- now run through all the local variables at this level of the lua stack
while true do
local name, value = debug.getlocal(2, i)
if name == nil then
break
end
-- this just skips unused variables
if name ~= "(*temporary)" then
variables[tostring(name)] = value
end
i = i + 1
end
-- this is what dumps info about a function thats been called
print((info.name or "unknown").. "(".. myUnpack(variables).. ")")
end
end
-- tell the debug library to call lua function 'hook 'every time a function call
-- is made...
debug.sethook(hook, "c")
-- call a function to try it out...
a_func("some string", 2012)
this results in the output:
a_func(asdf=2012, arg1=some string)
you can do fancier stuff to pretty this up, but this basically covers how to do what you're asking.
I have bad news, my friend. You can access function parameter names as they appear at the top of the function, but the data to access exactly what they were named in the calling function does not exist. See the following:
function PrintVariable(VariableToPrint)
--we can use debug.getinfo() to determine the name 'VariableToPrint'
--we cannot determine the name 'MyVariable' without some really convoluted stuff (see comment by VBRonPaulFan on his own answer)
print(VariableToPrint);
end
MyVariable = 4
PrintVariable(MyVariable)
To illustrate this, imagine if we had done:
x = 4
MyVariable = x
MyOtherVariable = x
x = nil
PrintVariable(MyVariable)
Now if you were Lua, what name would you attach in the metadata to the variable that ends up getting passed to the function? Yes, you could walk up the stack with debug.getint() looking for the variable that was passed in, but you may find several references.
Also consider:
PrintVariable("StringLiteral")
What would you call that variable? It has a value but no name.
You could just use this form:
local parms = { "MyVariable" }
local function PrintVariable(vars)
print(parms[1]..": "..vars[1])
end
local MyVariable = "bar"
PrintVariable{MyVariable}
Which gives:
MyVariable: bar
It isn't generic, but it is simple. You avoid the debug library and loadstring by doing it this way. If your editor is any good, you could write a macro to do it.
Another possible solution is add this facility your self.
The Lua C API and source is pretty simple and extendable.
I/we don't know the context of your project/work but if you ARE making/embedding your own Lua build you could extend the debug library with something to do this.
Lua passes it's values by reference, but unknown offhand if these contain a string name in them and if so if easily accessible.
In your example the value declaration is the same as:
_G["MyVariable"] = 4
Since it's global. If it were declared local then like others stated here you can enumerate those via debug.getlocal(). But again in the C context of the actual reference context it might not matter.
Implement a debug.getargumentinfo(...) that extends the argument table with name key, value pairs.
This is quite an old topic and I apologize for bringing it back to life.
In my experience with lua, the closest I know to what the OP asked for is something like this:
PrintVariable = {}
setmetatable(PrintVariable, {__index = function (self, k, v) return string.format('%s = %s', k, _G[k]) end})
VAR = 0
VAR2 = "Hello World"
print(PrintVariable.VAR, PrintVariable.VAR2)
-- Result: VAR = 0 VAR2 = Hello World
I do not give more explanation, because the code is quite readable, however:
What happens here is simple, you only set a metatable to the PrintVariable variable and add the __index metamethod that is called when the table is forced to search for a value in its index, thanks to this functionality you can achieve what you see in the example.
Reference: https://www.lua.org/manual/5.1/manual.html
I hope that future and new visitors will find this helpful.