Corona OOP multiple instances share properties

Question

I'm having a bit of a mental block about applying OOP to Corona. I've made a class which is a timepicker that I wish to re-use multiple times in my application. I tried putting two instances of it in the same storyboard scene, but the buttons on the first picker control the data and display on the second. So they are sharing data, functions, etc. I wonder if anyone can tell me where I'm going wrong? Here's my timepicker class (timepicker2.lua):

module(..., package.seeall)

-- include Corona's "widget" library
local widget = require "widget"

--decorator--------------------
function decorate(obj, hr, min) --object to decorate
print("--init new timepicker--")

theHour = 0
theMin = 0
am = true

function incHr(event)
    print("inc")
    if theHour < 12 then
        theHour = theHour + 1
    else 
        theHour = 1
    end

    if theHour < 10 then
        hrText.text = "0"..theHour
    else
        hrText.text = theHour
    end
end

increaseHrBtn = widget.newButton{
    default="gfx/up_regular.png",
    over="gfx/up_press.png",
    width=40, height=40,
    onRelease = incHr
}

hrText = display.newText("0", 10, 41, native.systemFont, 24)
hrText:setTextColor(0, 0, 0)

local decHr = function (event)
    print("inc")
    if theHour > 1 then
        theHour = theHour - 1
    else 
        theHour = 12
    end
    if theHour < 10 then
        hrText.text = "0"..theHour
    else
        hrText.text = theHour
    end 
end

decreaseHrBtn = widget.newButton{
    default="gfx/down_regular.png",
    over="gfx/down_press.png",
    width=40, height=40,
    onRelease = decHr
}
decreaseHrBtn.y = 100

dotsText = display.newText(":", 55, 39, native.systemFont, 24)
dotsText:setTextColor(0, 0, 0)

local incMin = function (event)
    print("inc")
    if theMin < 59 then
        theMin = theMin + 1
    else 
        theMin = 0
    end

    if theMin < 10 then
        minText.text = "0"..theMin
    else
        minText.text = theMin
    end
end

increaseMinBtn = widget.newButton{
    default="gfx/up_regular.png",
    over="gfx/up_press.png",
    width=40, height=40,
    onRelease = incMin
}
increaseMinBtn.x = 100

minText = display.newText("0", 90, 41, native.systemFont, 24)
minText:setTextColor(0, 0, 0)

local decMin = function (event)
    print("dec")
    if theMin > 0 then
        theMin = theMin - 1
    else 
        theMin = 59
    end
    if theMin < 10 then
        minText.text = "0"..theMin
    else
        minText.text = theMin
    end 
end

decreaseMinBtn = widget.newButton{
    default="gfx/down_regular.png",
    over="gfx/down_press.png",
    width=40, height=40,
    onRelease = decMin
}
decreaseMinBtn.y = 100
decreaseMinBtn.x = 100

local toggleAmPm = function (event)
    if am == true then
        am = false
        ampmBtn:setLabel( "PM" )
    else
        am = true
        ampmBtn:setLabel( "AM" )
    end
end

ampmBtn = widget.newButton{
    default="gfx/blank_normal.png",
    over="gfx/blank_press.png",
    label = "AM",
    font = "Korean Calligraphy",
    fontSize = 25,
    width=58, height=58,
    onRelease = toggleAmPm
}

ampmBtn.x = 160
ampmBtn.y = 58

if hr > 12 then
    if #hr < 2 then
        hrText.text = "0"..hr
    else
        hrText.text = hr
    end
    theHour = hr-12
    am = false
    ampmBtn:setLabel( "PM" )
else 
    if hr < 10 then
        hrText.text = "0"..hr
    else
        hrText.text = hr
    end
    theHour = hr
    if hr == 12 then
        am = false
        ampmBtn:setLabel( "PM" )
    else
        am = true
        ampmBtn:setLabel( "AM" )
    end
end

if min < 10 then
    minText.text = "0"..min
else
    minText.text = min
end
theMin = min

obj:insert(increaseHrBtn.view)
obj:insert(decreaseHrBtn.view)
obj:insert(increaseMinBtn.view)
obj:insert(decreaseMinBtn.view)
obj:insert(hrText)
obj:insert(dotsText)
obj:insert(minText)
obj:insert(ampmBtn.view)

end

and here's where I use it:

local reminder1Group = display.newGroup()
TimePicker.decorate(reminder1Group, 0, 50)
scrollView:insert(reminder1Group)

I have a feeling I need to tie the functions to the obj but am struggling with how exactly to do that. Hopefully someone can point me in the right direction? Many thanks!

EDIT!

Modified (and simplified) class so far:

module(..., package.seeall)

local widget = require "widget"

picker = {}
picker.__index = picker

function picker.new()
    local picker_object = {}
    setmetatable(picker_object,picker)

    pickerGroup = display.newGroup()

    picker_object.theHour = 0
    picker_object.theMin = 0
    picker_object.am = true

    picker_object.increaseHrBtn = widget.newButton{
        default="gfx/up_regular.png",
        over="gfx/up_press.png",
        width=40, height=40,
        onRelease = picker.incHr
    }

    picker_object.decreaseHrBtn = widget.newButton{
        default="gfx/down_regular.png",
        over="gfx/down_press.png",
        width=40, height=40,
        onRelease = picker.decHr
    }

    picker_object.decreaseHrBtn.y = 100

    pickerGroup:insert(picker_object.increaseHrBtn.view)
    pickerGroup:insert(picker_object.decreaseHrBtn.view)

    return picker_object
end

function picker:incHr(event)
    print("inc")
end

function picker:decHr(event)
    print("dec")
end

and where I call it:

local TimePicker = require("timepicker2")
local reminderPicker1 = TimePicker.picker.new()

... and now wondering how to get the physical aspects of this timepicker into a scrollview!

Answer 1

You haven't used OOP here! AT ALL! What you have done here is you have declared a function (albeit in a separate module) and called it.

Have a read here http://lua-users.org/wiki/SimpleLuaClasses and here http://lua-users.org/wiki/ObjectOrientationTutorial

Here's a gist of how you use OOP in lua(and hence Corona)

local animals = {}
animals.__index = animals

function animals.new(params)
  local animal_object = {}
  setmetatable(animal_object,animals)

  animal_object.name = params.name

  return animal_object
end

function animals:getName()
   return self.name
end

and here's how you use the class

local dog = animals.new{name="dog"}
local cat = animals.new{name="cat"}

local name = dog:getName()
print(name)   -- prints "dog"

local name = cat:getName()
print(name)   -- prints "cat

The thing you have to note is that when you call a function cat:getName as opposed to cat.getName (using semicolon instead of dot) you pass 'self' as an argument.
That self is the "object" of the class "animals"

'

Answer 2

I don't know the least thing about Corona, let alone it's OOP system, but the fact that you use globals in your function raises suspicion...

theHour = 0
theMin = 0
am = true

These are all globals, Lua uses the global per default paradigm. So unless you put a local keyword before them, they will be shared by your whole application.