I have a script file embedded in the Workspace that contains functions. I would like call these functions from script files embedded in child objects of the Workspace. I don't want to have to copy and paste these functions into multiple script files. I figured the object oriented approach would be best if its possible.
An alternative to _G is to use the also globally avaliable table, shared. Shared is used the same way _G is, but you must specify "shared" before the variable identifier, unlike _G, where you can merely write the name of the variable without the _G (not anymore in ROBLOX). Shared is used in the following context:
shared["variablename"] = value
Just like in the global stack, _G.
Example usage of shared:
Script 1
shared["rprint"] = function(array) for i,v in pairs(array) do print(i, v) end end
Script 2
repeat wait() until shared["rprint"]
shared.rprint({"Hello, ", "How", " are", " you?"})
The output of this script would be "Hello, How are you?"
The simplest way would be to use _G or shared.
In one script,
_G.myFunction = function(Arguments)
-- blah
end
In another script, you would use this code.
repeat wait() until _G.myFunction ~= nil
_G.myFunction()
This would also work with the global table shared, instead of _G.
I know it has been said before, but just use the normal _G or shared to access it.
Script one
_G.myFunction = function()
print("Hello, myFunction!")
end
Script two
repeat wait() until _G.myFunction()
_G.myFunction()
Output
Hello, myFunction!
I would use BindableEvents or RemoteEvents. I think this is a better approach than using _G. This will allow you to keep everything local. You can use Bindableevents and RemoteEvents to trigger functions and send as much data as you need back and forth between scripts. Use BindableEvents for server/server communication and RemoteEvents for server/client-client/server communications.
http://wiki.roblox.com/index.php?title=API:Class/BindableEvent
You can make the function global. In
one script do this:
_G.myFunction = function() print("Hello World") end
In another script do this:
repeat wait() until myFunction myFunction()
By defining a function is _G you must
wait for the script to execute
assigning the function, then you can
call the function even without
specifying _G.
This won't work because, due to ROBLOX updates, you now have to index _G whenever you access items inside it.
You cannot use dofile() in ROBLOX, either, as I saw mentioned above.
In answer to the question: you need to create a function in one script into the global table - _G, by adding _G.MyFunction = function(parameters) end. In another script, you need to access it inside the _G table - _G.MyFunction().
A common problem that appears for ROBLOX scripters is that you try to access your function inside _G before it is created. A simple way to solve this is to add a wait until it is created, as suggested from Camoy's post:
repeat wait() until _G.MyFunction()
You can make the function global. In one script do this:
_G.myFunction = function() print("Hello World") end
In another script do this:
repeat wait() until myFunction myFunction()
By defining a function is _G you must wait for the script to execute assigning the function, then you can call the function even without specifying _G.
You could use Module Scripts which were thankfully added. You could put the functions in there, then call and use them anywhere else!
Related
So I have scriptOne (module) and scriptTwo (local script I think). I use scriptTwo to require() and change the variables with that. But how do I update the values in scriptOne (that I also want to access from other scripts as well) to these new values?
scriptOne code
local module = {}
module.test = 100
while true do
wait(1)
print(module.test)
end
return module
scriptTwo code
local data = require(workspace.playerStats)
data.test = 0
changing variables inside of a modulescript is global, change a variable and every script using the module gets the new variable
the reason why the code you provided doesnt work is because of the while loop. the loop yields and cant proceed, meaning it cant also return the module so the server script is waiting forever.
The problem is the while loop in the ModuleScript. ModuleScripts are used by require() to share variables. In your case, your ModuleScript has a infinite loop, which doesn't let require() return, and gets the second script stuck. You are probably using the while loop for debugging the variable, so I'd recommend moving it to the second script.
Everybody knows that variables in Lua, if not explicitly defined as "local", will be global. This will sometimes cause problems, like overriding library functions, or unexpectedly providing a value for another global variable with the same name. So it should be very helpful if there's a way to find all global variables that is defined in a single Lua code file.
However, I failed to find any clue on this seemingly quite-popular problem. The best answer I can get online is using _G to print all global variables in the environment, which isn't of much help. I'm currently coding Lua in Intellij Idea with Emmylua, a powerful tool that can show global variables in a special style, and it can easily trace a global variable to its definition; but when the code becomes quite long, this will not help much either.
So basically, I just want to get a list of global variables defined in a given Lua code file. Either with a tool or with a wonderful function. If it can make things easier, we may presume the code file is a module. If it can further print the definition locations for these global variables, that's even better. Can somebody help me?
Lua doesn't have a way to tell when or where a global was introduced.
In the special that the value is a function, debug.getinfo may be able to help by telling you where the function is defined (which is often but not always the same place where the function is made global).
You can capture the needed information at the time the global is introduced. This can be done by setting a metatable with a __newindex method on the global table. This method will be called when a new global is introduced (but not when an existing global is overridden). In this method, you can figure out where the caller came from with debug.getinfo. Also beware, if any of your other code is trying to use a metatable on the global environment, you must play nicely with it. (It can only have one metatable.)
You can also avoid using the global table. One in-between way of doing this is to override the environment. In Lua 5.2 and Lua 5.3, this is done by declaring a local table called _ENV -- all accesses to the global table will instead access this table. (Actually, global accesses always use _ENV and _ENV is _G by default.) You can make this mostly invisible by giving this _ENV a metatable that forwards accesses to _G (or whatever other environment). The difference here is that __newindex will still be called even if a binding exists in _G, so this method can detect overrides.
Using _ENV, though is inherently local to a scope (e.g. each file needs to override it). Such a hook could be installed globally as well though. If you load your modules manually with the load function (unlikely), you can just supply a custom _ENV as an argument. If you use require, it is possible to get a hold of the loaded file before it is executed by overriding (or monkey patching) the Lua searcher in package.searchers[2]. This is the built-in function that require calls to find the file in your filesystem and then load it. The return value is the loaded function which require then runs. So, after it is loaded but before it is returned back to require, you could use debug.setupvalue to override the default _ENV value (if any).
Example code (only lightly tested):
local global_info = {}
local default_searcher2 = package.searchers[2]
package.searchers[2] = function(...)
local result = default_searcher2(...)
local parent_environment = _G
local my_env = setmetatable({}, {
__index = parent_environment,
__newindex = function(self, k, v)
local new_info = debug.getinfo(2)
-- keeping rich data like this could be a memory leak
-- if some globals are assigned repeatedly, but that
-- may still be okay in a debugging scenario
local history = global_info[k]
if history == nil then
history = {}
global_info[k] = history
end
table.insert(history, {info = new_info, value = v})
parent_environment[k] = v
end,
})
if type(result) == "function" then
debug.setupvalue(result, 1, my_env)
end
return result
end
function gethistory(name)
local history = global_info[name]
if history == nil then
print('"' .. name .. '" has never been defined...')
else
print('History for "' .. name .. '":')
for _, record in ipairs(history) do
print(record.info.short_src .. ": " .. record.info.currentline)
end
end
end
Note that the hook here will only apply to files required after this code has been run, and basically only applies to Lua files (not C libs) that get included via the built-in require. It doesn't set a metatable on the global environment, so not conflict there, but it could be circumvented if files access _G directly (or e.g. setup access to _G instead of _ENV in their own _ENV tables). Such things can also be accounted for, but it can be a rabbit hole depending on how "invisible" you need this patch to be.
In Lua 5.1, instead of _ENV, you have setfenv which I believe can be used to similar effect.
Also note that all the methods I'm outlining can only detect global accesses that actually get executed at runtime.
Yes. Local versus global is a binding issue, which is primarily established at compile-time. Setting a variable is, of course, well-determined at compile-time.
Lua provides the luac compiler, which takes the argument -l for list.
In Lua 5.1, there is the opcode SETGLOBAL. A column indicates the line number of the statement and the comment indicates the name of the global.
In 5.2 and later, there is the opcode SETTABUP. A column indicates the line number of the statement and the comment indicates the name of the table and key. "Globals" are in the table referenced by the _ENV upvalue.
So, you can easily find the line number of any statement that sets a global variable with the tools Lua provides.
BTW—under many module systems, a module script would not set any global variables.
I have a question from Lua/Roblox!
Basically, I want to fire a script from a script. This may sound like a stupid question, but actually it isn't :P
For example:
I have a script: script1 in ServerScriptStorage.
And, I want to code it to fire contents of script2.
Examples:
Content of script1:
game.Players.PlayerAdded:Connect(function()
HERE SCRIPT2 FIRING!
end)
Content of script2:
print("This message is triggered by event in script!")
This is fairly simple task I suppose, so please give me the SIMPLEST and SHORTEST version of code. I don't need any exclusives such like launching 2 script in 1. I'm a begginer script, so please keep it simple.
Thanks, NorteX.
In pure Lua, using dofile would probably make the most sense. However, in Roblox, the approach must be much different. The way I would recommend doing this is using a ModuleScript for "Script2". Then you would load the script using require(). Because "requiring" a script caches the returned value for future "requires", this means that the contents of the ModuleScript will only be executed once. Thus, if you have code you want to run multiple times, you should encapsulate it in a function that the ModuleScript returns.
Here's how the code would look like given your setup:
Script1:
local script2 = require(game.ServerScriptService.Script2)
game.Players.PlayerAdded:Connect(function(player)
script2()
end)
Script2:
-- In game.ServerScriptService.Script2 as a ModuleScript
return function()
print("This message is triggered by event in script!")
end
Check out the documentation for ModuleScripts to understand more about them.
workspace.SCRIPT2.Disabled = true -- Disables SCRIPT2 , you can remove this and manually disable it in SCRIPT2's properties.
game.Players.PlayerAdded:Connect(function()
workspace.SCRIPT2.Disabled = false -- Activates SCRIPT2. You can alter the "disabled" state multiple time to make it reboot and operate more than once.
end)
Also, you could replace workspace.SCRIPT2.Disabled by the location where your second script is, by example, workspace.FolderOne.scripts.SCRIPT2.Disabled . Just be sure it points to the script and keeps the "disabled" part on, so it knows to disable / enable it.
I just want to call some specific function in my Lua script.
A simple script:
msg("hello")
function showamsgbox()
msg("123")
end
I just want to let my C app call showamsgbox() only but not to run msg("hello") beacuse it will show a msgbox when i load this script! So how to do that to keep this situation away?
PS:it is just example.sometimes i want to let users make thier own plugins in my program.but I do not want them write something outside the functions(i want to use functions to decide what to do.for example function OnLoad() means it will be run when i load it ).If there is something outside functions i cannot control them!
You can't. The script defines two variables when run: a and geta. Recall that function geta()...end is the same as geta=function()...end.
The a = 9 will be called when the script is initially evaluated in a lua_State.
If you reuse that lua_State instance, you can retrieve the function and invoke it without re-initializing a.
It seems that you want to sandbox scripts. Just give them a suitable, separate environment before running them. It may be an empty one or it may contain references to the functions you want them to use. They can write at will in their environment and it will not affect yours. Then just get the value of OnLoad or whatever user function you want to call and call it.
I have an application that uses lua files for some of its more obscure configuration options. As such it mostly contains calls into the app to create things and alter properties; most C functions don't have a return value but some do.
I now have a need to read these same configuration files into a different application, and perform significantly different things when the functions are called (so I can't use common code). In addition, I'm only interested in a subset of the possible functions, and I think I can get away with by default ignoring (and/or returning nil) any other function call.
So I'm wondering what the best approach is here. How (from a C++ app), can I load and execute a lua script such that expressions etc are evaluated as normal but I can intercept and process certain app-defined C functions while simply ignoring (returning nil if required) calls to any other C functions?
(Note: I do have access to the vocabulary of the original app, which mostly uses luabind; I could just use the same definitions and change the implementation, but that's too fragile since the original app can have more functions added to it later. I would like something more generic.)
The goal is to get a bit of C code which I can use as a generic placeholder; the end result being "anything that's defined (standard library routines, functions defined in Lua, and C functions explicitly registered), call it as normal; for anything else, call one specific routine that simply does nothing, instead of raising an error". And preferably something compatible with luabind.
The whole process is initiated by a bit of C code that sets up the Lua environment, loads a set of files, calls one function, and then destroys the environment. There won't be anything ongoing.
Set a __call metamethod for nil:
debug.setmetatable(nil, { __call=function () end })
The _index metamethod for _G or other tables does not work because the name is resolved before the call.
(You don't need to use the debug API or library if you're setting this from C.)
How about using setfenv and a metatable? You can replace global environment table of certain function with an empty table. And then, set the placeholder function to ignore C-defined function.
local env = {} -- empty environment
local metatbl = {}
function metatbl.__index (tbl, key) -- provides placeholder function
return function()
print(key .. " called")
return(nil)
end
end
setmetatable(env, metatbl)
function samplefunc() -- your Lua code goes here
globalfunction "xyz" -- calls placeholder function
end
setfenv(samplefunc, env)
samplefunc()
If you want to use build-in function such as print, you can push it into env talbe like:
local env = {print = print}
If you have some way of differentiating the C functions from the ordinary Lua functions in your script, you can iterate over all functions defined in your Lua system, and for each C function that isn't on the list of functions you care about, replace that function's implementation with a simple nil-returning one. This is really easy if all the c-binding functions are defined tidily together in a table; if they're in _G you have a bit of a job ahead of you. The functions you do care about get bound via luabind as normal.