Scripting Helpers is winding down operations and is now read-only. More info→

Adding :Function() to an instance?

Asked by

Mokiros 135

9 years ago

I want to add a function to an instance, something like Part:Clone(). So how do i do it? Here what i want it to be:

1function Object:DoSomething()
2    --Do something to part
3end

You cannot add a function directly to an Instance. You can do that in a ModuleScript, however. Marios2 360 — 9y

2 answers

Answered by

BlueTaslem 18071

9 years ago

Edited 7 years ago

TL;DR: No. See below for what : means and why you can't add extra methods.

Sugars!

A function like part:Clone() is called a method.

Methods are just sugar for function calls:

`1`	`obj:func( x, y )` `-- EDIT: fixed typo`

is the same thing as

`1`	`obj.func( obj, x, y )`

That means I can do stupid things like this:

`1`	`workspace.Destroy( workspace.Part )`

which will, in fact, destroy workspace.Part.

How does a function get attached to an object? The same way any other value does.

01local object = {}
02 
03object.func = function(stuff)
04    print("Hi", stuff, "!")
05end
06 
07object.func("me")
08-- Hi me !
09object:func()
10-- Hi table: 0x12345

As another convenient sugar, Lua let's you define functions on objects without using =:

1function object.func(stuff)
2    print("Hello", stuff, "!")
3end

(Note that you can't use [] in function definitions like this, for some reason)

If you have a function that you generally expect to be a method, it would be nice to just write it out, instead of having to always write out the first parameter and make it look like a normal function.

Lua provides more sugar for that!

1function object:func()
2    print("Hello", self, "!")
3end

This implicitly defines self as the first parameter of the function. It's exactly the same as the previous definition, though, so I can still say

`1`	`object.func("BlueTaslem")` `-- EDIT: fixed typo`

`2`	`-- Hello BlueTaslem !`

Adding things to Instances

ROBLOX objects don't let you add new methods to them -- this is a result of not being able to add new properties to objects.

The good news about this is that when you invoke a method on a ROBLOX object, every script will agree on how to do it -- because ROBLOX says how to do it, not some script buried in your place that defined a different behavior.

If you want to make methods, you have to have your own objects!

You can "wrap" ROBLOX objects in order to extend their functionality -- create your object that exposes all of the things you want, and implement some of those in terms of an instance that you have:

01function MakeBlue(self)
02    self.part.BrickColor = BrickColor.Blue()
03end
04 
05function MakeRed(self)
06    self.part.BrickColor = BrickColor.Red()
07end
08 
09function Wrap(part)
10    assert(part:IsA("BasePart"))
11 
12    return {
13        part = part,
14        -- methods
15        MakeBlue = MakeBlue,
16        MakeRed = MakeRed,
17    }
18end
19 
20-- example
21local w = Wrap(workspace.Part)
22while true do
23    w:MakeBlue()
24    wait(5)
25    w:MakeRed()
26    wait(5)
27end
 View all 27 lines...

This should be the accepted answer. LetThereBeCode 360 — 9y

(typos are fixed now -- should no longer be misleading) BlueTaslem 18071 — 9y

can you use default methods on this though? creeperhunter76 554 — 7y

Answered by

LetThereBeCode 360

9 years ago

What you can do is make a table that holds the object that you want to run function onto. Then, add a method to the table.

1local Object = {obj = some_object_variable} -- change some_object_variable to a variable that holds your object
2 
3function Object:Transp(num) -- Here is an example function that changes the object
4    self['obj'].Transparency = num
5end
6 
7Object:Transp(0.5) -- Magick! :o

When you assign a method to a table, and it is called via colon (:), something happens in the background that you can't see. An argument is passed, self which holds the table variable that the method is called on.

Hope this helped.

lol this is sad iuclds 720 — 4y

Adding :Function() to an instance?

2 answers

Sugars!

Adding things to Instances

Answer this question