Unable to retrieve UUID in setEventHandler's callback

[glsubri]

Hello everyone.

I am using the ArduinoBLE library on my Nano 33 BLE.

I have a class, DayAlarmService which has three characteristics: enabled, startTime and duration. I have 7 instances of that class, one for each day of the week. I need to know on which one of them an event was triggered (like a read on a characteristic or a subscription, ...).

To do this, I have another class, AlarmServiceManager, which instantiates all 7 DayAlarmServices and stores all UUIDs (from the services and the characteristics). Since we have access to the BLECharacteristic when we set an event handler, I should be able to retrieve the uuid of the characteristic and check out to which day it corresponds. Of course, all characteristics and service have a different UUID, which are known by AlarmServiceManager.

The issue is that, for an unknown reason, when the callback is called, the uuid() function returns "random characters" and not the correct uuid. An example of the ouput is:

To make things easier, I have set up a few gists for you to view the code in question:

https://gist.github.com/glsubri/d5ed63afc946632d096ce7087aedc818
https://gist.github.com/glsubri/98516dad7d289ac1b0db14d35a6cf99d

This file contains multiple UUIDs definition:
https://gist.github.com/glsubri/f55c598d14261c36c40e17c20f87714a

The weird part is that I have other services and characteristics that can correctly access their uuid(). I don't understand why it doesn't work as expected in this case.

I hope that I was clear. If you need anything else, please let me know!

Thanks

P.S. I also have written something in Arduino's forum: https://forum.arduino.cc/t/unable-to-retrieve-characteristic-uuid-in-callback/882635

[polldo]

Hi @glsubri
The problem should be that your characteristics' UUIDs are allocated on the stack here
You could either give them a global scope, like you did for services' UUIDs, or allocate them on to the heap

[glsubri]

@polldo Oh, I see. I thought the uuids would be copied inside of the BLECharacteristic and BLEService.
I will probably store them in my AlarmServiceManager.

Thank you very much. I will get back to you when everything is working !

[glsubri]

So, everything seems to be fine when the uuids are stored statically.

However, wouldn't it make more sense if the BLECharacteristic and BLEService would be in charge of storing their uuid themselves (and copying it) instead of relying on other objects ?

[polldo]

That's a good point, can you make another issue to request this feature?
I'm going to close this one as it is solved.