feat(event-bus): Use instanceof check for of type operator

[yackinn]

No description provided.

[yackinn]

@michaelbromley Is this feature set fine for now?

[yackinn]

Let me know what we need tests for when we've agreed on an api for the event bus.

[michaelbromley]

Hi,

Thanks for your contribution :) I've spent a bit more time thinking about this. I'd like to only add the filter() method. The reasons are:

1. It is the most flexible.
2. I want to add as few new APIs as possible, as a general rule.
3. It's trivial to use a e => e instanceof MyBaseEvent predicate to get the ofInstance() functionality.
4. I think ofInstance() might cause confusion - it's not obvious by the name alone what the difference is between ofType() and ofInstance(). Both methods take a type - not an instance - as an argument. The distinction is quite subtle and it forces the user to think too much about the internal implementation details.
5. With .filter(), that implementation detail is made explicit in user code.

As this is a new feature, it should be made against the minor branch too.

For tests, you should add one or two tests to the event-bus.spec.ts file testing some predicate functions and asserting that events are correctly being filtered according to the predicate.

[yackinn]

@michaelbromley Please check and verify

[yackinn]

The typecast doesn't seem to be needed.

[yackinn]

Why are the jobs failing?

[michaelbromley]

The jobs are failing because of a config issue after I added the latest plugin - nothing to do with your code.

Thanks very much for your contribution!