Domoticz Community Forum - Support & Discussion

Posted: **Friday 14 July 2023 2:48**

In conditionals in Lua I read nil is considered false: https://www.tutorialspoint.com/lua/lua_ ... making.htm

For example if this sensor battery level is nil then this should be false and not fire:

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        if domoticz.devices('Garage side door sensor').batteryLevel < 100 then
                        
        -- do something
        end

Instead it errors out:

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2023-07-13 19:00:00.304 Error: dzVents: Error: (3.1.8) An error occurred when calling event handler Low battery notification
2023-07-13 19:00:00.304 Error: dzVents: Error: (3.1.8) ...s\dzVents\generated_scripts/Low battery notification.lua:61: attempt to compare nil with number

I did workaround it:

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        if domoticz.devices('Garage side door sensor').batteryLevel ~= nil and domoticz.devices('Garage side door sensor').batteryLevel < 100 then
                        
        --do something
        end

I noticed that dzVents / Lua is somewhat lagging Lua itself so I'm not sure if that is the issue?

https://www.lua.org/versions.html#5.4

Posted: **Friday 14 July 2023 8:08**

Not all sensors supports .batteryLevel
Have few motion sensors with such problem.
Check documentation on sensor

Posted: **Friday 14 July 2023 9:27**

user4563 wrote: Friday 14 July 2023 2:48 In conditionals in Lua I read nil is considered false: https://www.tutorialspoint.com/lua/lua_ ... making.htm

For example if this sensor battery level is nil then this should be false and not fire:

Wrong assumption: you are not evaluating the sensor battery level, but are comparing nil with a number. That raises -correctly- an error.
Read the Lua manuals and try it yourself in Lua.
There's a diffence between:
1. evaluates correctly

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local a = nil
if a then print('ok') else print('not ok') end

and:
2. raises an error

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local a = nil
if a < 10 then print('ok') else print(not ok') end

Try it.

Posted: **Friday 14 July 2023 21:53**

I see what you mean. I assumed nil is false regardless but it's actually only like a boolean false.

Thank you for the information!

Posted: **Saturday 15 July 2023 11:46**

i don't see your point. it would not work anyway. Neither nil nor false are automagically converted to numbers.

Code: Select all

> print( false > 17 )
input:1: attempt to compare number with boolean

Posted: **Tuesday 18 July 2023 3:45**

"Lua programming language assumes any combination of Boolean true and non-nil values as true, and if it is either boolean false or nil, then it is assumed as false value. It is to be noted that in Lua, zero will be considered as true."

Posted: **Tuesday 18 July 2023 11:37**

Yes. It works only one way. All values are implicitly converted to boolean. Most convert to "true".
But boolean and nil values are not converted to numbers. They cannot be compared to number values without error.

Posted: **Tuesday 18 July 2023 14:58**

Thank you everyone for your knowledge!

Domoticz Community Forum - Support & Discussion

nil is supposed to be false in conditionals but errors in dzVents

nil is supposed to be false in conditionals but errors in dzVents

Re: nil is supposed to be false in conditionals but errors in dzVents

Re: nil is supposed to be false in conditionals but errors in dzVents

Re: nil is supposed to be false in conditionals but errors in dzVents

Re: nil is supposed to be false in conditionals but errors in dzVents

Re: nil is supposed to be false in conditionals but errors in dzVents

Re: nil is supposed to be false in conditionals but errors in dzVents

Re: nil is supposed to be false in conditionals but errors in dzVents