Callable not behaving as expected

darthpejka

Hi folks,
So I've run into a bit of an issue where I thought this should be possible with Callable and anonymous functions, but I'm getting an unhelpful error message from the engine so I'm not sure what exactly the problem is.
The setup is basically this: when a boss is ready() I create a list of commands that are called in sequence. Basically a command pattern, and these command objects then apply whatever functionality they have to, return a timer, once that's done, onto the next. It works perfectly, but I need the ability to switch between these patterns based on certain conditions (e.g. a component has been destroyed), so I tried something like this:

Which in my mind, should work. But I'm getting the following error:

What am I missing here? I have an alternative I know will definitely work, but that would be much less flexible and I like this idea, so any help would be appreciated.

xyz

darthpejka What exactly are you trying to test with conditional != null. An "empty" callable object will not evaluate to null because the callable object itself exists
Check:

var c: Callable
print(c == null)
print(c)

If you need to determine validity of the callable, use Callable::is_null() and/or Callable::is_valid()
That said, you still haven't provided enough context to deduce where the bug actually is.

DaveTheCoder

What is the line of code that causes that error message?

darthpejka

DaveTheCoder

It's the line if conditional.call() == true.
Also to note, it does run and evaluate to false at first (which it shouldn't as warp_ring is still valid) - it switches to the else branch, runs two commands in the alt_pattern, and only when it would cycle back to the original pattern does it throw the error.

DaveTheCoder

darthpejka

In 4.4-beta3, I just tried using "!= null" for a Callable, and it didn't work correctly.

is_instance_valid() didn't work either.

Try printing the value of conditional before that line:
print_debug("conditional=",conditional)

darthpejka

DaveTheCoder
So I typed up a response as I started to suspect that Callable cannot be null, but just to make sure whether this is a bug or intended, I searched a bit and I found this: https://github.com/godotengine/godot/issues/72209
Seems like this is intended behaviour, and it can be fixed by using something like this instead:
if not conditional.is_null():
This fixes the error, now it's just that the conditional evaluates to false when it shouldn't. But otherwise the flow is at least proceeding smoothly!

darthpejka

xyz
Yeah, just realized that a few minutes ago.
And just as I wanted to type down my current issue, I realized the problem was that my anonymous function's return type was void, and not returning anything -_-
Now it looks like this: EnemyCommandSwitchPattern.builder().condition(func() -> bool: return is_instance_valid(warp_ring)).new_pattern(1).alt_pattern(2).build()

And it works beautifully.

Thank you both for your help!