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:
function Object:DoSomething()
--Do something to part
end
✓ ANSWER ACCEPTED
Adding :Function() to an instance?
2 answers
✓ Accepted answer
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:
obj:func( x, y ) -- EDIT: fixed typo
is the same thing as
obj.func( obj, x, y )
That means I can do stupid things like this:
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.
local object = {}
object.func = function(stuff)
print("Hi", stuff, "!")
end
object.func("me")
-- Hi me !
object:func()
-- Hi table: 0x12345
As another convenient sugar, Lua let's you define functions on objects without using =:
function object.func(stuff)
print("Hello", stuff, "!")
end
(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!
function object:func()
print("Hello", self, "!")
end
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
object.func("BlueTaslem") -- EDIT: fixed typo
-- 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:
function MakeBlue(self)
self.part.BrickColor = BrickColor.Blue()
end
function MakeRed(self)
self.part.BrickColor = BrickColor.Red()
end
function Wrap(part)
assert(part:IsA("BasePart"))
return {
part = part,
-- methods
MakeBlue = MakeBlue,
MakeRed = MakeRed,
}
end
-- example
local w = Wrap(workspace.Part)
while true do
w:MakeBlue()
wait(5)
w:MakeRed()
wait(5)
end
3 comments
0
This should be the accepted answer.
0
(typos are fixed now -- should no longer be misleading)
0
can you use default methods on this though?
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.
local Object = {obj = some_object_variable} -- change some_object_variable to a variable that holds your object
function Object:Transp(num) -- Here is an example function that changes the object
self['obj'].Transparency = num
end
Object: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.
1 comment
0
lol this is sad
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1 comment
You cannot add a function directly to an Instance. You can do that in a ModuleScript, however.