Pre/Post hook and lifecycle

[Solido]

This is an evolving discussion around previous/current value of a signal
and how pre/post check hook can influence the connection and help manage lifecycle.

Currently if you want to access previous value of a subscribed signal you have to

$signal.subscribe((v) {
      final previous = $signal.previousValue;
      doSomething(previous) then ...
});

Signature would have been much better with subscribe(previous, current) for chaining.

$signal.subscribe((previous, current) {
     doSomething(previous) 
});

Can be expressed with elegance when non required

$signal.subscribe((_, current) {
      
});

Maybe a real consideration for people pushing Signals it a lot of sugar to not repeat the var and less error prone.

As a general remark Signals should get inspired (copy without questions) functional signatures and move away from oop.

equalityCheck can be hacked in the meantime, it has the right signature but come on ;D

[rodydavis]

This could be done via a set of extension methods without having to update the type signature!

[Solido]

The idea never touched my mind
Thanks a lot for the feedback!

I'm digging about something more general,
like hooks so we can act pre and post update.

[rodydavis]

Signal hooks for sure. I think that would be possible in general and would love to add support for it.

It could be a wrapper signal that adds the functionality just like a change stack too

[Solido]

Most of the logic is already there!

Signal handle transmission but you just need confirmation/infirmation upfront and lifecycle of previous signal. When you switch to a new signal value you may have to handle resources not in the signal itself but the previous value. It should be handled before managing effects of the new value.

[Solido]

I don't know if it could be a wrapper or direct implementation.
Like equality check it should be able to trigger events but also, at least pre, be able to cancel the assignation.

[rodydavis]

I am leaning towards the wrapper because I want the default to be max performant and have various extensions (or mixin) for various uses cases.