Global Functions: Difference between revisions

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Have you ever wondered how things like :Remove() and :Clone() always work, even though you've never indexed it? Here's how:
{{CatUp|Tutorials}}
__TOC__


If you know how to use the _G[] (global) command, this might come more easily to you than others. This is basically how a global command works:
== Introduction ==
Global functions are function accessible in all environments and threads.  Global functions must be contained within what is called the global environment which is represented by a table called the global table.  _G is the variable that holds the global table.  In ROBLOX _G works differently than in normal Lua. In ROBLOX you must index values from the global table if you set them.


<pre>_G["Bob"] = game.Workspace.Bob</pre>
{{Example|<syntaxhighlight lang="lua">
_G["foo"] = "bar"
print(_G["foo"]) -- bar
</syntaxhighlight>}}


If you're in a ScriptBuilder, you can exit that script and open a new one. Put this in it:
Any function, and any thread can access the "foo" variable so long as the example code is run before the other thread is executed.


<pre>Bob.Torso:Remove()</pre>
== History ==
Sometime in 2010 it was decided that _G was a security issue. Before this date all threads could read and write to the global table.  Instead, a substitute table was put in place of _G.  This was a table called "shared".  All threads could access the "shared" table, however you must actually index it:


run that script, and your torso gets removed! Why? Because the _G[] (global) command makes "Bob" availible in every script. Now, to get a global function:
{{Example|<syntaxhighlight lang="lua">
shared["foo"] = "bar"
print(shared["foo"]) -- bar
</syntaxhighlight>}}


<pre>_G["Lazer"] = function(person) person.Torso:Remove() end</pre>
The way _G worked before allowed this:


Now exit that, and do this:
{{Example|<syntaxhighlight lang="lua">
_G["foo"] = "bar"
print(foo) -- bar
</syntaxhighlight>}}


<pre>Lazer(game.Workspace.Bob)</pre>
Values within the _G table would be replicated into all the threads environments, not just the _G table itself.
 
If your character's name is, "Bob," you should have your torso removed.


[[Category:Scripting Tutorials]]
[[Category:Scripting Tutorials]]

Latest revision as of 04:53, 27 April 2023

Up one category:
Tutorials

Introduction

Global functions are function accessible in all environments and threads. Global functions must be contained within what is called the global environment which is represented by a table called the global table. _G is the variable that holds the global table. In ROBLOX _G works differently than in normal Lua. In ROBLOX you must index values from the global table if you set them.

Example
_G["foo"] = "bar"
print(_G["foo"]) -- bar


Any function, and any thread can access the "foo" variable so long as the example code is run before the other thread is executed.

History

Sometime in 2010 it was decided that _G was a security issue. Before this date all threads could read and write to the global table. Instead, a substitute table was put in place of _G. This was a table called "shared". All threads could access the "shared" table, however you must actually index it:

Example
shared["foo"] = "bar"
print(shared["foo"]) -- bar


The way _G worked before allowed this:

Example
_G["foo"] = "bar"
print(foo) -- bar


Values within the _G table would be replicated into all the threads environments, not just the _G table itself.

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