Type hinting for event aruments

[xorik]

Hi.

I'm trying to understand correct way to hint types for events. Now only this is working for me:

const player = new ex.Actor(0, 0, 30, 30, ex.Color.White)

player.on('preupdate', (event: any) => {
  const evt: ex.Events.PreUpdateEvent = event
})

When I try to use correct type, tsc throws a error:

player.on('preupdate', (event: ex.Events.PreUpdateEvent) => {
  // logic
})
// Argument of type '(event: PreUpdateEvent) => void' is not assignable to parameter of type '(event?: GameEvent<any> | undefined) => void

Is there way to avoid the "any" type and the second variable?

Thanks

[Erik Onarheim]

Hi Xorik,

Feels like a bug, this seems to be a factor of typescript strict function type and strict null checking. Excalibur as a project pre-dates this typescript compiler feature, in fact we probably would have noticed this when we implemented this https://github.com/excaliburjs/Excalibur/issues/1143.

As a temporary workaround, disabling this check in the tsconfig.json removes the error, however this is definitely unideal if contravariant functions and strict null check types are important to you.

One other workaround to capture the appropriate type due to strict null checks in the handler, and add a typeguard.

I've opened an issue in excalibur to address this issue specifically

https://github.com/excaliburjs/Excalibur/issues/1147 

Thanks for asking! We'll get this sorted.

Erik 

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