Having problem detecting valid MQTT event on PicoW

[Simon Walters]

I tried using not (lastEvent) but that didn’t work - the say was still executed every loop iteration (It says false)

So I tried doing a comparison of lastEvent <> false - that didn’t work either

So, ended up testing the length for non-zero and that worked

But, I feel the 1st one should have worked

PEBKAC or something else :)

Simon

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[Bernat Romagosa]

This sounds like a type issue. In MicroBlocks you can only broadcast strings, but you’re comparing a message against a boolean.

Can you test whether my hypothesis is right?

[Simon Walters]

I'm out and about but I'm not broadcasting the message, it's being received as MQTT message inside a loop. The say block outputs the text false when no message to process but looking for that text or Boolean false doesn't seem to work.

[Bernat Romagosa]

Interesting. That text may contain some hidden character that you’re not seeing. Can you maybe print the unicodes for the message and see if there’s anything weird in there?

[Simon Walters]

I'll try that out when I get home

[Simon Walters]

So adding this in when length = 0 gives [0 item list]

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[Bernat Romagosa]

Yes, when length == 0 that makes perfect sense. My hunch was that the non-empty message would contain some other hidden character. That is, maybe 'false' is not just 'false' but maybe 'false\n', for example. That would cause your (message) == 'false' comparison to fail.

Do I make sense? :)

[Simon Walters]

What you say makes sense :)

My issue was that the say block outputs false but testing for false doen't work

I think lastEvent must always be a list and is zero length when no message available.

I think there might be an issue with the say block reporting false instead of

[image: image.png]

But, I'll just carry on testing for length=0 and sleep well at night :)

[John Maloney]

Sorry for the slow response. I've been away from email for the holidays.

You just need to compare with boolean value false, not with string false:

The "not" version that you tried first doesn't work because MicroBlocks only considers the boolean value "true" to be true; any other value is considered "false" (i.e. not true). That is in contrast to some programming languages that consider any value that is not false, zero, or NULL/Undefined to be true. Thus "not" of any value except the boolean true (including lists, numbers, and strings) is always true.

[Simon Walters]

I’m glad there is a logical (pun intended) explanation as to why not(lastEvent) didn’t work :)