New "datatype"

Garry's Mod coding
#1

How do i create my own “datatype”? I know in a language like java its called a class, but how do i do it in lua? I never see it done… I am trying to recreate and optomize source’s entity networking, but to do so i need a datatype to return. How can i make one that i can call a function on? Like… example:
[lua]
local NewEnt = NewNet.Create(“prop_physics”)
NewEnt:CallSomeFunction()
[/lua]

Thanks in advance :stuck_out_tongue:

#2

metatables

#3

Thanks

Edit: Whats this business about __index?? Do i need it?

#4

__index redirects to a table or function when the table you setmetatable is referenced/indexed/accessed/whatever, basically passing what you want to pass instead of the table itself.

#5

Very sorry… im probably a retard or something… but what the hell did you just say?

#6

Haven’t messed with metatables much myself, but it’s something along the lines of this.

[lua]local tbla = {}
tbla.wat = true

local tblb = {}

setmetatable(tblb , {__index = tbla})

print(tblb.wat)[/lua]

#7

Read this: http://www.lua.org/pil/16.html

It can’t get any clearer, once you’ve read the whole chapter several times, manipulating metatables will be easy as fuck.

#8

Which one can i make methods on? Like… im confused. What is tbla and tblb? What IS a metatable anyway?

#9

A metatable is quite literately, data about data. It’s information about how a table should be handled.

#10

Alright maby i don’t mean a metatable. I want to have an object that has properties and methods i can call on it, and i can return one etc.

#11

Yeah, you do use metatables for that. For example, Angles and Vectors in GMod are made with metatables, unless I’ve cocked up and mixed them up with something else…

#12

Can i see the source for them?

#13

I think they are at least. I’m not sure. I’m too busy to check if they are in the gcf or not.

#14

Where can i find the source for them?

#15

Probably somewhere in the GCF.

There’s an example there.

#16

Okay, that was very helpful. Thank you.

#17

If it is only going to be called on entities then you can use…


local ENT = _R.Entity

which is equivalent to


local ENT = getmetatable("Entity")

then you can create the functions like


function ENT:DoSomething()
   self:DoSomeStuffToIt()
end

It just helps speed things up for us lazy people :wink:

#18

Do you even know what metatables really is? thats very unrelated

#19

[lua]
a = {}
print(a.b)
[/lua]
This will print nil, since b is undefined.
[lua]
c = {}
c.b = “hurr”
a = {}
a.__index = c
print(a.b)
[/lua]
This will print “hurr” because when it can’t find a value for index b in table a it looks in table c since that’s what __index is set to, there it find that b is equal to “hurr” and thus return “hurr” to the print function.

__index can also be a function.
[lua]
a = {}
a.__index = function(self,key) --self is always equal to a

return "You tried to index "..key.." but it was nil."

end
print(a.b)
[/lua]
Prints “You tried to index b but it was nil.”
If you don’t understand this just read it again and again 'til you do:smile: