Absolute beginner's guide to scripting

This tutorial will get you started on learning how to script using the Lua language to help bring your games to life.

[edit] What is scripting?

Scripting is a way of telling the computer what to do. However, computers can only understand commands to do things if you tell them exactly what to do, in a specific code or language. In this case, the language we're going to be learning how to use is called Lua, which is relatively simple to understand.

A key addition to Roblox Lua is the ability to navigate a tree of objects in your game using a parent-child relationship between objects (don't worry if you don't understand what that means!)

[edit] Before proceeding...

  • It's Lua, not LUA. Lua means "Moon" in Portuguese.
  • Reading itself is not as effective as doing what the guide tells you to do and typing the code. In other words, practice every other thing you learn - if not every new thing. It's a lot at first, but it's not hard to get through it after you've done it several times.


Contents


[edit] Your first program

You are about to make your very first script - a script to kill your character. There are multiple ways to run code in ROBLOX, but you will be executing the script from a place in ROBLOX Studio called the command bar. The command bar allows you to run a script instantly in a blank place. The first thing you want to do, is open up the command bar, which is in ROBLOX Studio.

How do I open Studio, and how do I enable the command bar?
  • Windows XP
    1. Click the button at the bottom left of your screen with the Windows logo and the word "Start" next to it.
    2. Hover your mouse over "All Programs".
    3. Locate the folder "Roblox". Hover over that.
    4. Click "Roblox Studio".
  • Windows Vista/7
    1. Click the Windows logo at the bottom left corner of your screen.
    2. Click "All Programs".
    3. Locate the folder "Roblox". Click that.
    4. Click "Roblox Studio".
  • Windows 8
    1. Click the very bottom left hand corner of the screen. The start menu will show up.
    2. Type "Roblox Studio". A list of applications will show up. Click the appropriate application.
  • Mac OS X
    1. On the Dock, click the Applications folder (folder with an "A" printed on it).
    2. Locate "RobloxStudio", and click that.
  • Enabling the Command Bar
You can enable the command bar by going to: View > Toolbars > Command (if there is no check mark next to it). A text box will appear at the bottom of the software. You can insert code in there and it will execute.

[edit] Being specific

When you first create a script, you have to know what it is meant to do at exactly what time and under what conditions. For a script that kills your character, it's pretty obvious what it needs to do; kill you. Scripting is giving commands to the computer, so you just need a line of code that will kill your character.

Remember that scripts can break with just one letter or symbol being wrong.

Before we go on, you may or may not know that there is an object inside each character called the Humanoid. It is an object that holds certain properties, like the amount of health and the maximum amount of health, how fast the character walks, and a couple of others. So, how do you kill your character? There are many ways, actually. If the Head and Torso are detached from each other, the character is dead, so deleting the head or the torso is a possible solution. It is even possible to set the Humanoid's health to 0 manually. We'll delete the head.

ROBLOX won't remove anything until told, so we need to navigate the tree structure of ROBLOX games to find the character's head and remove it. The structure of a ROBLOX game is like a tree, and the trunk is a DataModel object called game. There is a "branch" (known as a child) called Workspace. Think of all the bricks in your game as children of Workspace. Your character is a child of the Workspace, and the Workspace is a child of game.

Note: For the example below, game is hidden, which is the reason why it is invisible when looking through Studio. There are more necessary objects that are required in the tree, but this is here to provide a visual example.
  • Tree-collapse.png
    DataModel
    game
    • Tree-collapse.png
      Workspace
      Workspace
      • Expand.png
        Model
        Player
        • Part
          Head
        • Humanoid
          Humanoid
    • Tree-collapse.png
      Players
      Players
      • Expand.png
        Player
        Player

Note that children of game are known as game services, which provide functionality for your game automatically. When you enter any place, you have a Player object named after you inside the Players game service and a model named after you in the Workspace (called a character). Your character holds your head, torso, limbs and other visual stuff. The player object does other things that won't be covered right now.

ROBLOX Studio has a nice tool that lets you view the family tree visually. It is called the Explorer window. To open it, click View > Explorer. It is very self explanatory.

[edit] Writing Lua code

The ultimate trick to being a scripter is to mastering how to make code that does what you want, when you want it to. Since you are a beginner, you will be walked through the steps to making your code do what you want starting from English to Lua code. Do not think of scripting as translating to a language; think of scripting as giving orders on what to do.

Here's our starting command. It's what we want to happen, and it has been written in plain English.

Remove USERNAME's head.

Naturally, ROBLOX will not like that very much because it's in English! You have to figure out how to express what you want to happen in Lua code.

Remove Head, which is in Player, which is in Workspace, which is in game.

game is the root of all things in your game. We need to "go down" the family tree and find the correct brick to remove. To get an object that is a child of another object, you use a period (.) after the parent object, then the child object's name. Going through the family tree, we get this:

Delete game.Workspace.USERNAME.Head

This is almost a working ROBLOX Lua statement! Now, to actually remove the head, a method must be used. Methods are functions that do specific things in ROBLOX for you by calling them. Methods are functions of objects in ROBLOX Lua. To call a method on an object in Lua, you use a colon (:) after the object. You then state the name of the method, then two parentheses with nothing in them. Methods and functions take arguments, which are values given to the function to change how it works. The "Destroy" method takes no arguments, so we place the parentheses there to show that there's nothing else we have to pass on to the Destroy method.

game.Workspace.USERNAME.Head:Destroy()

The above statement is syntactically correct Lua code. However, your name isn't USERNAME, so substitute your name in. If your name was "AwesomeSocks", then you would use the following:

game.Workspace.AwesomeSocks.Head:Destroy()

To compare this to English, it would be like saying "The sky has trees". It is grammatically correct English, but an untrue statement. If you state the name of things that do not exist, your script won't work and an error will occur.

[edit] Testing the script

To test your newly created script, enter any normal ROBLOX place in solo mode (or build mode) so that you can walk around with your character. Open up Roblox Studio and open the command bar. Type your one-lined wonder in, and hit enter to run it.

NOTE: You must open build mode or solo mode from the studio, if you open it from the browser, you will not be able to open the command bar.

If your head just disappeared and you heard an "Oughh!" sound because your character just died, then you have succeeded. Your script works.

If your script does not work and nothing happens, expect this to happen a lot. Scripters (and programmers alike) run into the problem of their scripts not doing something right because their code has bugs in it. Not to worry, though - there is the output, a key tool that can help you debug your scripts and get them working.

[edit] Setting Values in ROBLOX Lua

What about changing values of objects in ROBLOX Lua? There is a way to do that, and it's more of the same. To set your health to zero (rather than going "Off with your head!") you need to set the Health property of your Humanoid to zero. To set properties of objects, you use a period (.), the property's name, an equals sign and the value.

game.Workspace.USERNAME.Humanoid.Health = 0

You will learn specifics about what is what in ROBLOX Lua later (such as "What does the equals sign really do?"). For now, you can consider yourself a really basic scripter that can call methods and change property's values.

Protip: The Workspace is a special game service. Since it is used a lot in scripting, ROBLOX Lua has a built-in constant (just like game) called Workspace rather than game.Workspace. You'll learn about constants and variables later, but know that the Workspace is the only object in ROBLOX Lua that has it's own built in constant. You can therefore do this:

Workspace.USERNAME.Humanoid.Health = 0

[edit] Inserting a Script object

To add a new script in ROBLOX Studio, just select Workspace in the Explorer window and click Insert > Object > Script. You'll find a blank script that has been added to the Workspace.

Insertscript.JPG

So, the hierarchy would be:

  • Tree-collapse.png
    Workspace
    Workspace
    • Script
      Script

Try modifying it to do different things. It is similar to the command bar we have been using, but now you can have multiple lines of code.

[edit] Editing a script in ROBLOX Studio

To open a script object's source (the code in the script object) for editing in ROBLOX Studio, you can double-click it in the Explorer window and a text editor will open where you can change your script's source. Whatever you add, remove or change in this text editor is permanent, and besides the "undo" button, these changes cannot be undone once the editor is closed.

[edit] Starting and Stopping your script

Script objects run their code under the following conditions:

  • The script is added to the game (Select the script in the Explorer window and cut it (CTRL+X), then paste it back into the game (CTRL+V, or right click Workspace and click "Paste Into").
  • The script's disabled property is changed to false (select the script in the Explorer window and toggle it's Disabled property in the Properties window).

[edit] Script Creation

There are 5 topics that will be answered here:

  • Creating the script
  • Storing references to objects
  • Listening to events
  • Functions
  • Modifying objects

NOTE: All work, building and scripting, should be done in Edit Mode. All these lessons will be shown as if you are in Edit Mode. To open Edit Mode, on your desktop screen, hit Start>Programs>ROBLOX>ROBLOX Studio. Then go to your profile or place page or places list, then click "Edit". You can also press CTRL+N or click File>New to get a completely empty place.

[edit] Creating the Script

To get a script, go in Roblox Studio and then simply select Insert>Object. Now, a window will appear. In the newly appeared window, click on "Script" and OK. You should find the script inside "Workspace" in the explorer tab. If you don't see any explorer window up, go to View > Explorer.

Now to open the script, just double-click it. If you did it right, a window will cover the whole ingame screen. And you will find the line "print "Hello World!"" Before you start, just go ahead and delete that line.

[edit] Making References to Objects

Assuming the script is still under Workspace, that is where your script will run. Let's say you want a brick turning invisible/visible, back and forth when touched. The script needs to know where that brick is before modifying it.

Now, making references to objects is not necessary, but it can make scripting a lot less work. Here's an example of how you do it:

local brick = Workspace.Brick

That will make `brick` refer to game.Workspace.Brick. You can set the name to absolutely anything. This is an example of a variable. You can have as many variables as you want in a script.

If you didn't store it in a variable, every time you try making the script modify the object, you would have to put the line "Workspace.Brick". Variables make it much simpler, since you only have to put the name you assigned. Name the brick desired to "Brick", and make a reference to it in the script by typing the example above. Note that making a reference to an object is the same as assigning a variable.

[edit] Event Listeners

Now we're getting into the meat of scripting. Sure, the script knows where the brick is, but that's all. It can't do anything else. Now we're jumping into a listening event.

An event listener watches what's going on, and waits for an event to happen. When it does, it tells the script to do something. This is one important part of the script, otherwise you couldn't really make scripts wait for anything.

You still should have the script with the variable in it. We're going to make the script listen for being touched (the Touched event). Here's an example:

brick.Touched:connect(onTouch)

When the brick is touched, it will execute the function named onTouch. Keep in mind that the name inside the parentheses is the name of the function.

This is not the only listener type. There are many more to use, some of which require some familiarity with scripting. Here is a very well-done reference page set up by MrDoomBringer.

This is where you can find more help in the future, when you begin to understand scripting more. Not only does it show Events, but also shows other scripting references need for other aspects of scripting.

Put the line
brick.Touched:connect(onTouch)
a line or two below the variable assignment
local brick = Workspace.Brick

[edit] Functions

Your script is getting better and better, but where is the function? Your script will break if it doesn't have one of those for the listener to refer the script to.

What is a function? It is where all your modifying work will be done. It is also an important part to your scripting. Without it, you could not make the script modify objects from listeners. Another example:

function onTouch(part)
 
end

There is the function. As you can see, the word "function" is followed by "onTouch", the name of the function. The listener from last lesson is trying to refer to the function. The listener is going to tell the script to run through this function and do whatever is found inside. Notice the "(part)" after the function name. This is a reference to the object that the listener found that touched the brick. This is not needed for event listeners but will allow you to have more objects to manipulate.

But back to what we're looking at. The variable "part" is the object that touched the brick. You can play with this object for fun later. Now notice also two lines below the function: "end". You will need one of these for every function and other block structures in scripting, such as "if" statements. Always remember this when scripting.

Now, make the lines from first example, except put it two lines under the variable assignment, and one line above the listener.

[edit] Modifying Objects

The script knows the brick, will wait until it's touched, and has the function to use. But it doesn't know what to do to the brick.

This is where storing references to objects saves you time. We wanted it to flicker invisible/visible, so here's an example:

brick.Transparency = 1 
wait(1) 
brick.Transparency = 0

These lines will alter the brick as we wanted. The brick's transparency is changed to "1", which is completely invisible. The "wait(1)" line will make the script wait for one second before continuing, then the brick's transparency will be put back at 0, which is completely visible. You can alter "wait(1)" to any number inside the parentheses. Whatever number you put inside the parentheses will be the amount of time it will wait in seconds.

Put those 3 lines right under the line "function onTouch(part)" and above the line "end".

[edit] Complete script

local brick = Workspace.Brick -- Store a reference to the brick.
 
function onTouch(part) -- The function that runs when the part is touched.
	brick.Transparency = 1
	wait(1) 
	brick.Transparency = 0 
end 
 
brick.Touched:connect(onTouch) -- The line that connects the function to the event.

[edit] Advanced scripting techniques

[edit] Make your own functions

Main article: Function#Using Functions

While scripting, you may want to make your own function to call later. This is easy enough, here is the syntax (grammar) for doing so: (NOTE: These functions are called without a colon [:])

function functionName(parameters)
	code
end
 
functionName(arguments)

[edit] Functions with Parameters and Arguments

A parameter is a way to give data to a function. An example of a parameter: you use the TakeDamage method on a Humanoid. You have to tell it how much damage to do. You would type Humanoid:TakeDamage(100) to damage the Humanoid by 100.

NOTE: The TakeDamage method will not take damage if the humanoid has a ForceField. Use this method for weapons instead of directly setting the health, to prevent spawn-killers)

Example
function sayHello(name)
    print("Hello, " .. name .. "!")
end
 
sayHello("Bob")
Hello, Bob!


[edit] Functions that return values

Main article: Function#Using Return

The return statement automatically ends the function at the line it is placed (you still need to use the end statement though), and then gives the value to the variable on the left side of the equals sign.

Example
--Declare a function called addNumbers with the parameters "a" and "b"
function addNumbers(a,b)
    --make a variable called "ans", and set it to the sum of a and b.
    local ans = a + b
    --Return the variable called ans.
    return ans
end
 
--Declare a variable called "answer" to the value of the addNumbers function, with the arguments 1 and 2.
answer = addNumbers(1, 2)
--Print the answer to the output.
print(answer)


[edit] Flow control

Flow control, or Control statments basically means doing different things depending on the situation. They can also control the way the code is executed in the end. There are two main ways to do it in Lua, both involve conditions.

[edit] Conditions

A condition is an expression that either equals true or false. Conditions are usually used in if statements, though not always. A condition can never be placed by itself. Here are some simple conditions:

if 1 == 2 then

Note the "==". "==" is for comparison like this, and "=" is for assignment like assigning a variable a value.

Of course 1 isn't 2! So that would be false.

if 1 < 2 then

That would be true, because 1 is less than 2.

[edit] If statements

Main article: Conditional statements

The if statement does something only if a condition is true.

Syntax:

if (condition) then
	code
end
Example
if 2 + 2 == 4 then
print("All is right in the world")
end


That would print "All is right in the world", because 2 + 2 is equal to 4.

There is also an else statement, which executes if the condition is false:

if (condition) then
	code
else
	code
end
Example
if (2 + 2 == 4) then
print("All is right in the world")
else
print("Warning! Warning! Computer Self-Destruction!")
end


[edit] While

Main article: Loops#While
while <condition> do
	code
end

This does something over and over until the condition is false, or the break command is executed. Here is something very important: If this is an infinite loop, you MUST put a wait() function in your loop! Otherwise the server will take every ounce of its processing power to execute the code, because right when it's done, it wants to execute again. Having no wait() function WILL crash the server if it doesn't pause. This will make it wait so it has time to execute other things.

Example
while true do
	print("Lagging up your computer...")
end


That will crash the server, or it could crash your client. If it's a normal script, then that script will apply to the server, hence it will crash everybody in the server. If it's a LocalScript, then it will only crash the corresponding player's client. The LocalScript can be ran if the script is parented in the player's Character, PlayerGui, or Backpack.

Example
while true do
	print("Still lagging, but not crashing")
	wait(1)
end


That will print "Still lagging, but not crashing" on the output every second, until the script is disabled, or if a break statement is used.

[edit] See also