Persisting variable states

Developer's Corner General Dev Discussions
#1

I am trying to create the following scene:

Turn off lights when there has been no motion in the room for 30 minutes

local lul_tmp = luup.variable_get(“urn:micasaverde-com:serviceId:SecuritySensor1”,“Tripped”,31)
if(lul_tmp=“1”)
then
varTimes= varTimes+1
else varTimes=0
end

if (tonumber(varTimes)>29)
then
luup.call_action(“urn:upnp-org:serviceId:SwitchPower1”,“SetTarget”,{ newTargetValue=“0” },17)
varTimes=0
end

I will call this scene every 1 minute via timers

Anyone knows if the state can be remembered between calls?

Thank you

#2

http://wiki.micasaverde.com/index.php/Scripts_for_scenes

#3

Doesn’t that mean the sensor is tripped?

#4

As shown in @Ap15e’s reply, you’ll want to set a variable on the device using luup.variable_set for it to persist. As an added bonus, this will survive a reboot of Vera, whereas setting global Lua variables doesn’t.

Global variables do persist for as long as the Lua interpreter runs. I use one in the Caddx alarm plugin to maintain a copy of the alarm system state. The trouble is that the lifetime of a Lua interpreter on Vera is not especially clear for things other than full-fledged Luup devices.

Also, your Lua code has a bug, using = for comparison; in Lua, use == for comparing two values for equality.

(Digression: In the linked example “Scene that runs only if a security sensor has been tripped for a set period of time”, I’m not sure that it’s good style to be creating variables in the “urn:micasaverde-com:serviceId:SecuritySensor1” namespace. Probably the code should be using its own private namespace for the TripPeriod variable.)

#5

There’s no problem in creating variables in existing services, because they are created only for the current device. So if I create a variable in the SecuritySensor service for the device #3, other devices won’t be able to see it because it wouldn’t exist for them. The namespaces are per device, not per service.

#6

Agreed, but that wasn’t my point. My point is that if I go around creating variables in someone else’s namespace, then I am assuming that that the owner of that namespace will never, not even in the future, add a variable with the same name (and probably a different meaning). If I use my own namespace then this isn’t going to happen.