Okay…I got it.
inside the table would be like this
local myTable =
{
so and so
la la la
}
correct?
Keep telling me what is next
so and so
la la la
is important 
Maybe it will help if I write globaldata.lua
[lua]
local score = 0
local myData = {}
myData.GetScore = function()
return score
end
myData.AddToScore = function(num)
score = score + num
end
return myData
[/lua]
Now main.lua
[lua]
local dataStore = require( “globaldata” )
local myScore = dataStore.score – you will get nil because score from globaldata.lua is invisible in other files
local myScore = dataStore.GetScore() – it will return 0
dataStore.AddToScore(5) – now score will be 5
print( dataStore.GetScore() ) – it will give you 5 as expected
[/lua]
now you can in other file do
[lua]
local dataStore2 = require( “globaldata” )
print(dataStore2 .GetScore()) – will print 5 
[/lua]
I do get the 5 – but I don’t really understand it.
First I change the function like this
function myData.GetScore () return score end
I’m use to do it this way, I think is the same … right?
Then…
I’m looking at the globaldata.lua file
you are creating a variable score
and a table myData
2 separate things.
you also are creating 2 functions
What I don’t really get is the “dot” stuff
I know a function has a name
like
local function name ( )
but I don’t get the
local function name.something ( )
and then, when you call a function
I do this
name ( ) – I just use the name of the function to run the code, inside the function
but I don’t see the “call” in main.lua
by the way…
Thank you very much for taking the time to teach me this
from the bottom of my heart, thank you
What I don’t really get is the “dot” stuff
If so, read first about tables in Lua.
You just make function part of the table simply speaking.
but I don’t get the
local function name.something ( )
It’s rather something.name()
but I don’t see the “call” in main.lua
[lua]
dataStore.GetScore()
dataStore.AddToScore(5)
[/lua]
but this are calls
just do a google search
‘tutorial on lua scope’
plenty of examples
Hi guys.
I think I’m getting a little bit.
Finally I got to make it work.
Thanks
Here’s the link to the Corona SDK external modules tutorial:
http://www.coronalabs.com/blog/2012/08/28/how-external-modules-work-in-corona/
I’m going to read this with more time
to try to understand it. – so far I don’t really get it.
But that is not what I need.
If I have a variable named – imageA = 100
normally I write
local imageA = 100
then I can use imageA in my file.lua
If I want to use imageA, inside of a function, then I have to remove the local
imageA = 100
then I can use imageA, inside the function or another function or ANYWHERE in my file.lua
I need to use the same imageA = 100
in a different file2.lua
or in file7.lua
or in pageBackUp.lua
So the question is how do I write the variable, to use it in all my files.lua?
Hi Victor,
We strongly discourage the use of global variables, especially since there are simple and clever ways to avoid them. Please read this tutorial on the matter:
http://www.coronalabs.com/blog/2013/05/28/tutorial-goodbye-globals/
Brent
An external module is exactly what you need. It will persist between pages as long as you don’t specifically get rid of it. I use them all the time.
Create globaldata.lua
[lua]
local this = {}
this.someDataToKeep = nil
return this
[/lua]
In page1.lua
[lua]
local globaldata = require( “globaldata” )
globaldata.someDataToKeep = 9999
[/lua]
In page#.lua
[lua]
local globaldata = require( “globaldata” )
local savedPoints = globaldata.someDataToKeep
[/lua]
Cheers.
still confuse…
Tell me if I’m thinking the correct thing.
I have to create another file (module) like – myData.lua
Do I have to put all this in the file?
display.setStatusBar( display.HiddenStatusBar ) local storyboard = require "storyboard" storyboard.purgeOnSceneChange = true storyboard.gotoScene( "home" )
or this
local storyboard = require( "storyboard" ) local scene = storyboard.newScene()
or nothing…
Then do I have to write this?
--my global space local M = {} return M
If so then I write the variables or the functions under…
--my global space local M = {} return M local scoreObject local score = 0 local glow local function addToScore(num) score = score + num scoreObject.text = score end local function resetScore ( ) score = 0 addToScore(0) end
or I have to remove the local like this:
--my global space M = {} return M scoreObject score = 0 glow function addToScore(num) score = score + num scoreObject.text = score end function resetScore ( ) score = 0 addToScore(0) end
And then I can use the addToScore function in any other file.lua
is that more or less correct?
All wrong, so slowly
First I would recommend you to read about variables scope in Lua
But shortly:
If you write [lua] local var[/lua] but not in function (scopes), Lua will create variable accessable in whole file it was declared.
If you ommit’local’ it will create variable in space (called global) which is accessable wherever in program, however it is strongly discouraged as it’s not efficient and pollutes code.
If you want to expose content of file outside, you must use ‘return’ keyword (as in function). However it is better ( if you have a lot of variables and functions) to wrap it into something as table.
So at the top of the file we create table with
[lua] local t = {} [/lua]
Next we create variable we want to expose, but we declare it as table key
[lua] t.glow = 5 [/lua] (in lua you can also asign function this way, as t.func = function() end)
At the end of file we must return our ‘t’
In other file if we do [lua] local lib = require (“name of the file with table t”) [/lua], returned table ‘t’ from file will be assigned to variable ‘lib’ (as you would call function and assign value returned by it)
Now under variable ‘lib’ you have reference to table in other file so you can do [lua] local a = lib.glow * 5 [/lua], you can also modify it, because ‘lib’ is now reference to ‘t’ not just copy (tables always are passed by references)
If you would write [lua] local glow [/lua] in file with ‘t’ but wouldn’t make it part of returned table ‘t’, lib.glow would return empty nil because it wasn’t part of returned table
Hi develephant. adn Brent, and everyone else
– I know this post it’s long. Please read it, it’s important to understand. —
Thanks for the post. I’m Trying to understand this new concept. it’s hard…
I did just like you told me, word by word
–create a new file globaldata.lua
–inside I created the table you said – this {}
–then I put the .someDataToKeep to the table – I put the file inside the folder, where I have the main.lua file.
Then in page1 – for me it’s the very first page that I see, main.lua is sending me to this page first.
this page I have the name of home.lua
In home.lua I put this
local storyboard = require( "storyboard" ) local widget = require "widget" local scene = storyboard.newScene() local globaldata = require( "globaldata" ) globaldata.someDataToKeep = 9999
So I requiere the globaldata and add a number to the someDataToKeep.
Then in another page… page1 I tried this.
–I requiere the globaldata again…
and put this
local savePoints = globaldata.someDataToKeep local function letsSee () print(savePoints) end letsSee()
To see if it works…
I run the program, and in the console it writes
9999
So it works!
But I still have the same problem with the scores, I don’t really get how to make the scores work.
I ask you please, to be patience with me, I’m doing my best.
In pageR I have a score function and variables that make the score works
–I got this from the videos I bought from Jay White. – the ones they have in Corona.
scoreObject score = ud.someData local glowCoin function addToScore(num) score = score + num scoreObject.text = score end function resetScore ( ) score = 0 addToScore(0) end [code] So inside a function a use the call addToScore(10) [code] if plant.x == 670 then transition.to(plant, {time=100, x=670, y=406}) plant:removeEventListener ("touch", plantTouch) audio.play(win) coinPlanta.isVisible = true transition.to(coinPlanta, {time=1000, x=glowCoin.x, y=40, onComplete=glow}) addToScore(10) end
And it adds 10 points to the scoreObject – this is perfect.
But when I go to another page … page1 or page4 or page6
I don’t know what to do to “keep adding points”
If I put the call addToScore(20) – the program tells me is a “nil” value
because the addToScore it’s not there.
But If I do the same thing that I did in pageR
then it resets to 0 and adss only the 20 new points, so it’s not adding more extra points.
When you know how to do things it’s really simple
but right now I’m just going crazy.
Please help me out
Hi piotrz55.
I’m trying to understand.
You make it sound simple.
but my head and my brain are not that advanced yet!, sorry!
Please read the above post, to see if you can explain things in
a little bit different way, to help me understand.
I think I can understand it, I just need to make my brain get it.
I think with your help, form all of you.
I will get this new challenge.
Thanks for your patience!
If it’s hard, lets break it down
First I suggest you leave storyboard and widgets for now because it’ll make it somehow harder to understand overall.
Ask step by step what isn’t clear and we’ll try to solve it, even if it’s the most basic one. If still not clear, I’ll try to rephrase again
But must know your programming experience if any (mainly languages)
okay…step by step…I like that.
I have a folder.
inside that folder I have the main.lua file to start the app.
I have the requiere storyboard in main.lua and that takes me to home.lua – another file/module
In there I have 3 variables to add score or points.
– scoreLabel – where I have the image of the word “score”
– scoreObject – here is a number “0” it’s an object that changes as it gets more points.
– score = 0 – this is a variable named score and that has 0 points
in the same home.lua file I have right under those 3 variables, 1 functions
function addToScore(num) score = score + num scoreObject.text = score end
This function is to pass a number
so when I call the function to run…
I use this command…
addToScore ( ) – but Inside the parenthesis I add the points I want to give to the player, like this:
addToScore(10)
the function I use is this
if plant.x == 670 then transition.to(plant, {time=100, x=670, y=406}) plant:removeEventListener ("touch", plantTouch) audio.play(win) coinPlanta.isVisible = true transition.to(coinPlanta, {time=1000, x=glowCoin.x, y=40, onComplete=glow}) addToScore(10) end
And it works, it adds 10 points and in the variable … I see now 10, where before was a 0
So far so good.
All I need, it’s to be able to go to another file/module, not home.lua
let’s say page2.lu, and call the addToScore (20) function and add the points
10 in the home.lua plus 20 in the page2.lua
and I will have 30 points in the scoreObject.
I need the storyboard because I have many files in my app.
The problem is when I go to page2.lua and call addToScore
it gives me a nil value.
because page2 does not have the function name “addToScore”
so that’s why I get nil
I hope this will explain things a little bit better.
Programming experience – not much.
I have 2 apps in the app store already, they are very simple apps
but very nice. Actually I have sold about 300 of one of them
“Piano For Kids Level 1”
For me 300 it’s a lot, I’m very happy.
That’s why I want to learn more
so I can make better apps
Right now I just want to be able to add points to the score
all the games have that, I thought, it was not going to be too hard
but it seems it is really difficult.
Thanks for your help.
No, no - wait. As I said, leave storyboard for now. We must first resolve concept of making modules and variable scopes
Okay…
You tell me what to do
I do want to learn
Just leaving storyboard will be enough
Let’s strip your main to empty file and create globaldata.lua
in globaldata write
[lua]
local dataTable = {}
– place for some code here
–
return dataTable
[/lua]
and in main write
[lua]
local myExternalData = require( “globaldata” )
[/lua]
everything in one folder
Let’s see what happened. When Corona starts it always executes main.lua and main.lua only - it’s important.
If you want to get content from other file you must load it’s content somehow.
When you written
[lua]
local stroyboard = require(“storyboard”)
[/lua]
you have done exacly the same as we’ve done with local myExternalData = require( “globaldata” ) line
require() function loads file’s code into memory and returns data if any - as in function, if we want something to be returned, we use ‘return’ at the end. In storyboard case it return table with bunch of functions. We also returned table, but for now empty.
Is it somehow clear up to this point?