Function return handler

function createStausBar(data)
   --code here
   return handler
end

a = createStausBar(data)

a.setMaxValue(5)
a.setValue(3)

local handler = {}
function handler.draw()
--do stuff
end
return handler

theoriginalbit, on 20 May 2014 - 02:02 PM said:

then yes your best route is to make use of metatables :)/>

apemanzilla, on 20 May 2014 - 02:04 PM said:

Of course, OOP is always better ;)/>

theoriginalbit, on 20 May 2014 - 02:11 PM said:

apemanzilla, on 20 May 2014 - 02:04 PM said:

Of course, OOP is always better ;)/>

Eh, not always. OOP isn't the only design pattern in the world of programming.

flaghacker, on 20 May 2014 - 04:25 PM said:

Thanks, I'm going to read some oop tutorials!

apemanzilla, on 20 May 2014 - 04:31 PM said:

flaghacker, on 20 May 2014 - 04:25 PM said:

Thanks, I'm going to read some oop tutorials!

Make sure you understand meta tables first :P/>

a={}
b={}
b.test = 17
setmetatable(a, {__index=b})
print(a.test)

obj:func(args)

obj.func(obj,args)

local function getHandler (text)
  local handler = {
    text = text or "default text"
  }

  handler.getText = function ()
    return handler.text
  end

  handler.setText = function (newText)
    handler.text = newText
  end

  return handler
end

local handle = getHandler("Hello")

print(handle.getText()) -->> Hello

handle.setText("World!")

print(handle.getText()) -->> World!

MKlegoman357, on 21 May 2014 - 07:37 AM said:

Spoiler

You don't really need to use metatables for this:

local function getHandler (text)
  local handler = {
	text = text or "default text"
  }

  handler.getText = function ()
	return handler.text
  end

  handler.setText = function (newText)
	handler.text = newText
  end

  return handler
end

local handle = newHandler("Hello")

print(handle.getText()) -->> Hello

handle.setText("World!")

print(handle.getText()) -->> World!

--# I'm using the do block here to hide the `prototype` table from outside scopes
--# we don't want anything gaining direct access to that, we want them to access it via a handler
local newHandler
do
  local prototype = {}

  function prototype:getText()
    return self.text
  end

  function prototype:setText(text)
    self.text = text
  end

  newHandler = function(text)
    local ivars = {
      text = text or "default"
    }
    return setmetatable(ivars, {__index = prototype})
  end
end

local helloWorld = newHandler("Hello")
local fooBar = newHandler("foo")

print(helloWorld:getText())
print(fooBar:getText())

--# change helloWorld text, fooBar text will stay the same
helloWorld:setText(helloWorld:getText() .. " World!")

print(helloWorld:getText())
print(fooBar:getText())

theoriginalbit, on 21 May 2014 - 08:43 AM said:

MKlegoman357, on 21 May 2014 - 07:37 AM said:

Spoiler

You don't really need to use metatables for this:

local function getHandler (text)
  local handler = {
	text = text or "default text"
  }

  handler.getText = function ()
	return handler.text
  end

  handler.setText = function (newText)
	handler.text = newText
  end

  return handler
end

local handle = newHandler("Hello")

print(handle.getText()) -->> Hello

handle.setText("World!")

print(handle.getText()) -->> World!

MKlegoman357:17: attempt to call nil

in any case, it is better to use OO for that, you can reuse the functions as opposed to creating a bunch of functions in memory.

OO Example

--# I'm using the do block here to hide the `prototype` table from outside scopes
--# we don't want anything gaining direct access to that, we want them to access it via a handler
local newHandler
do
  local prototype = {}

  function prototype:getText()
	return self.text
  end

  function prototype:setText(text)
	self.text = text
  end

  newHandler = function(text)
	local ivars = {
	  text = text or "default"
	}
	return setmetatable(ivars, {__index = prototype})
  end
end

local helloWorld = newHandler("Hello")
local fooBar = newHandler("foo")

print(helloWorld:getText())
print(fooBar:getText())

--# change helloWorld text, fooBar text will stay the same
helloWorld:setText(helloWorld:getText() .. " World!")

print(helloWorld:getText())
print(fooBar:getText())

take note of the use of the colon syntax however. If you wish to use the dot notation you must either do helloWorld.getText(helloWorld) or make use of a handy little script I made here which you would replace the local prototype = {} with. That little script allows you to invoke functions either with the colon syntax or dot notation without having to supply the table (if you do however that is fine).

local glass = peripheral.wrap("right")
glass.clear()
local frontArgs = { 1, 1, 50, 50, 0xFF0000, 0 }


function createBox(frontArgs)
	local newHandler
	do
		local prototype = {}
		--Variables
		prototype.frontHandler = glass.addBox(unpack(frontArgs))
		--Functions
		function prototype:setWidth(value)
			self.frontHandler.setWidth(value)
		end		
		--Main
		newHandler = function(text)
		local vars =
			{
			text = text or "derp"
			}
		return setmetatable(vars, { __index = prototype })
	  end
	end
end

testHandler = createBox(frontArgs)
testHandler:setWidth(500)

test:28: attempt to index ? (a nil value)

flaghacker, on 21 May 2014 - 02:49 PM said:

–EDIT2:
Oh you're not supposed to put everything in a function, it is already a function…

glass:102: attemp to index ? (a nil value)