Limiting number of multi-select (query) options possible

I need to limit the number of options that a user can selecting a query - drop-down multi select field.

In:
www.joomlapolis.com/forum/87-presales/234523-hide-options-in-a-cb-query-based-on-selected-options-in-a-previoius-cb-query

Nant mentioined:

Not with CB Query by itself and not dynamically.
You could use a CB Auto Action to check if more than 3 options were selected and then either keep the first three selected or display some error message.

Is there any trigger that would be 'onAfterFieldChange' (or something like that)? (so we could trigger some code that counts the values selected as they select)?
or
Does the 'onBeforeUserProfielSaveRequest' happen before when the user clicks the update button from a profile edit? (so we could do the validation before the data is saved)

Also ... do you have a list of all the Triggers, explaining exactly when they are called? (Some of the names I'm not sure when they happen by their title)

Also, do you have a 'getting started with Auto Actions' document or video?
I couldn't find one that gives a good introduction to AutoActions (just a few use-case examples that don't really explain how everything works)

We don't have any functionality in CB to limit the selection. A custom validation plugin would be best case, but jQuery can be used to limit the select. This however won't apply any restrictions on the PHP validation. A multi-select is stored as |*| delimitered. So a code action can be used to explode it and count the results and that's how many are selected or you could count the occurrences of |*| then add 1.

Also ... do you have a list of all the Triggers, explaining exactly when they are called? (Some of the names I'm not sure when they happen by their title)

No, we've only the reference below. Triggers are typically named obvious to what they do. Some of the older triggers in core CB may not be as obvious, but all newer triggers should be. With that said when in doubt simply ask as we're here to help.

www.joomlapolis.com/documentation/279-community-builder/tutorials/18358-using-cb-triggers

Also, do you have a 'getting started with Auto Actions' document or video?
I couldn't find one that gives a good introduction to AutoActions (just a few use-case examples that don't really explain how everything works)

We have the below videos with various usage examples.

www.youtube.com/playlist?list=PLp0puRITgC7McQcw0Sli1qfSUQGwmflzi

Thanks for the tips.
(Not sure HOW I missed those videos).

Also, for anyone reading this in the future, this is how I managed to implement the selection restriction.

For the (query multi) field that needs to be limited:

Create a INTEGRATIONS | CB CODE FIELD validation (enable the validation).

Then use the following code:
This works in multiple fields (i.e. you can just paste this code into multiple query fields and it will work with all.
You can change the number in the 4th line (i.e. "4") to one more than you want to have the limit set (limit of 5 - set to 6, etc.)

NOTE: This does NOT provide a live validation. Although I tried using the "Ajax Validation", it didn't have any effect (probably because I only have PHP code here).

If someone is able to improve this code (or make it function with real ajax validation) please share your solution.

Thanks again to the CB team. I couldn't have done this with any other extension. (And believe me, we tried )

The ajax usage should work. Does it just do a swirl animation icon then nothing? Ajax validation should only trigger if the value has changed from its previous value as well. You can use $value (also have access to $user and $field) or [value] to access the value the user supplied.