Question

I was following this tutorial http://www.crawlspacegames.com/blog/inheritance-in-lua/ and created 2 objects (drums and Guitar) that inherit from MusicalInstrument. Everything worked fine until I added timer functions, then for some reason only 1 from the 2 objects that inherit from MusicalInstrument gets called

MusicalInstrument.lua:

module(...,package.seeall)

MusicalInstrument.type="undefined"

local function listener()
print("timer action: "..MusicalInstrument.type)
end

function MusicalInstrument:play(tpe)
    MusicalInstrument.type = tpe;
    print("play called by: "..MusicalInstrument.type)
    timer.performWithDelay(500,listener,3)
end

function MusicalInstrument:new( o )
    x = x or {} -- can be parameterized, defaults to a new table
    setmetatable(x, self)
    self.__index = self
    return x
end

Guitar.lua

module(...,package.seeall)
require("MusicalInstrument")

gtr = {}

setmetatable(gtr, {__index = MusicalInstrument:new()})

return gtr

Drums.lua

module(...,package.seeall)
require("MusicalInstrument")

drms = {}

setmetatable(drms, {__index = MusicalInstrument:new()})

return drms

main.lua

--    CLEAR TERMINAL    --
os.execute('clear')
print( "clear" ) 
--------------------------


local drms=require("Drums")

drms:play("Drums")

local gtr=require("Guitar")

gtr:play("Guitar")

This is the terminal output:

clear
play called by: Drums
play called by: Guitar
timer action: Guitar
timer action: Guitar
timer action: Guitar
timer action: Guitar
timer action: Guitar
timer action: Guitar

I excepted the output to have 3 guitar time calls and 3 drums timer calls

Any ideas on how to make this work will be appreciated much!!

Thanks

—————————– Edited after another try ——————-

The following change in MusicalInstrument

module(...,package.seeall)

MusicalInstrument.type="undefined"

function MusicalInstrument:listener()
print("timer action: "..MusicalInstrument.type)
end

function MusicalInstrument:play(tpe)
    MusicalInstrument.type = tpe;
    print("play called by: "..MusicalInstrument.type)
    timer.performWithDelay(500,MusicalInstrument:listener(),3)
end

function MusicalInstrument:new( o )
    x = x or {} -- can be parameterized, defaults to a new table
    setmetatable(x, self)
    self.__index = self
    return x
end

Resulted with the following output :

clear
play called by: Drums
timer action: Drums
play called by: Guitar
timer action: Guitar

The correct instruments were called by the timer but only once

Answer 1

In both listener and MusicalInstrument:play() you write and read the same variable for both instances.

You actually want to set the instrument type per instance here. Lua is not exactly my primary language, but e.g. something like:

function MusicalInstrument:listener()
    print("timer action: "..self.type)
end

function MusicalInstrument:play(tpe)
    self.type = tpe;
    local f = function() self:listener() end
    timer.performWithDelay(500, f, 3)
end