Generic Event Registration

[dull galleon]

I have the following struct:

pub struct FullTimerFireRequest<T: FullTimerFireRequestType> {
    pub affecting_timer_set_policy: AffectingTimerSetPolicy,
    pub timer_to_fire: T,
}```

The following lines throw an error as I don't specify the type:
```impl Plugin for FullTimerFireRequestPlugin {
    fn build(&self, app: &mut App) {
        app.add_event::<FullTimerFireRequest>();
    }
}```

Does that mean that in order to implement the event for all types that implement `FullTimerFireRequestType` I'd have to add a separate event for each one of them?

[barren hill]

yes

[dull galleon]

I was thinking of

1. Have a specific plugin that'll register all events for a specific type
2. Make a "type iterator" though I couldn't make it work

[barren hill]

A plugin would definitely work, just make it generic and then you can just add the plugin and it adds the event and whatever else you need for you :)

@dull galleon ping for visibility

[dull galleon]

So something like an EventRegistrator<T> that registrates all relevant events for this type

Interesting

[barren hill]

yep, something like this:

struct EventRegistrator<T: Event>(std::marker::PhantomData<T>);

impl<T: Event> Plugin for EventRegistrator<T> {
    fn build(&self, app: &mut App) {
        app.add_event::<T>();
    }
}

the Phantomdata is only needed if you won't use an instance of T

[dull galleon]

So I actually used that but I'm having problem registring that plugin within other plugins

not sure what's wrong tbh, it says I should try to add a value and not an object but I'm just feeding it the T the bigger function gets

[barren hill]

what error do you get?

the first thing i can think of is that SendableTimerFireRequestType doesn't have the same trait requirements (or whatever they're called) as the one that FullTimerFireRequestPlugin needs

[dull galleon]

it's exactly the same one
(The full timer fire request plugin also takes T: SendableTimerFireRequestType)

[barren hill]

it's hard to know what the problem could be without seeing the error

[dull galleon]

true, turning on the computer now so I can copy it

[barren hill]

do you have Default implemented?

try calling ::default

when adding the plugin

[dull galleon]

I don't have default for the plugin

[barren hill]

the problem is that the plugin has a field, so you need to construct an instance of it

currently you're just giving it the struct itself

so either implement Default, or implement your own functions like new, or just construct it

[dull galleon]

The error remains

[barren hill]

and then do

app.add_plugins(FulltimerFireRequestPlugin::<T>::default());

[dull galleon]

oh I see

Well, now it says that T has to implement default which would mean making sure each variant always has a default value

(thinking)

maybe I'll just make the phantom an Option

That
did not work

new() time

[barren hill]

#[derive(Event)]
struct MyEvent(f32, i32, String);

struct MyPlugin;

impl Plugin for MyPlugin {
    fn build(&self, app: &mut App) {
        app.add_plugins(EventRegistrator::<MyEvent>::default());
    }
}

struct EventRegistrator<T: Event>(std::marker::PhantomData<T>);

impl<T: Event> Plugin for EventRegistrator<T> {
    fn build(&self, app: &mut App) {
        app.add_event::<T>();
    }
}

impl<T: Event> Default for EventRegistrator<T> {
    fn default() -> Self {
        Self(Default::default())
    }
}

this works for me

and MyEvent is not implementing default

[dull galleon]

yea my bad I should have implemented Default by hand rather than just add the derive one

I wonder if I should make a macro for that

because the entire phantom and default boilerplate isn't really important

well, that should do