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Please look at the below Lua script.

Idea is, before changing the status, am getting the current status by calling "getStateFlag()" and assigning to "status" variable. Methods ChangeState1 or ChangeState2 can change the current status. So later when calling ResetStatus method I can reset to old status by assigning stored value of "status".

But issue is, this "status" variable always sets to 0.

function Start()
    status = 0
    local flag = getStateFlag()
    if(flag == 1) then
       status = getCurrentStatus()
       ChangeState1()
    else if(flag == 2) then
       status = getCurrentStatus()
       ChangeState2()
    else
       ResetStatus(status) 
    end
end

function ChangeStatus1()
     device::set_value(1)
end

function ChangeStatus1()
     device::set_value(2)
end

function ResetStatus(status)
     device::set_value(status)
end
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1
  • Consider editing your question to describe the environment you're running in (it sounds like some sort of embedded processor?). If other users have experience with it, they may have ideas. Commented Mar 26, 2016 at 1:02

3 Answers 3

Reset to default
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So if I understood your question correctly you will call Start() multiple times. If flag equals 1 or 2 you want to store the current status value and then it will be altered inside ChangeState1() or ChangeState2() Else you want status to be reset to the value from your last call to Start() But currently it will be 0 every time you call Start() without flag being 1 or 2.

So basically you only want to initialize status with 0 when it is not defined yet.

What you can do inside Start() is this:

status = status or 0

So if status is nil it will default to 0, otherwise it will remain unchanged.

Or you simply initialize status outside the functions.

A cleaner solution would be to separate your backup status from the value that is changed by ChangeState1 or ChangeState2. So you will only access your backupStatus variable when you want to back it up or you want to restore it. otherwise you use some currentStatus variable.

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5 Comments

This complete script will run for each time when I click a button. So, if the status has value, then it should not assign to 0 on next execution... is there any way ?
@Roe yes do as I explained.
I have tried status=status or 0... but the value of status is 0 always. I think the value of status is initializing each time when this script runs.
did you delete the line status = 0? of course when your global scope is lost the value of status will be lost as well.
yes I deleted status = 0 and now I have status = status or 0 . So is there a way to persist the value of a variable when the same script runs again?
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But issue is, this "status" variable always sets to 0.

First of all you should separate two distinct values - previously saved status, and current status you get with getCurrentStatus(). Now you mixed them both in single variable, which gets initialized with 0 every time you enter Start() function. When you're not asking current status (i.e. flag is not 1 or 2), you actually destroy previously saved value with status=0 assignment.

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This script will run on a button click. So, each time this script runs, it assigning status =0 as I have declared like this. Anyother way to keep this value as constant?
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Based on the comments in Piglet's answer, it sounds like the problem here is that your runtime environment is deleting or clearing your global variables between each run. You could verify that by printing the value of status at the beginning of Start() (assuming you have some way to get output). If it's always nil, that's a pretty good indicator you're losing the global state each time.

If that is the case in your environment, you'll have to find another way to store state across runs. You may have access to a filesystem or some external storage specific to the platform.

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