如何使用预定义的管道运算符导出 rxjs 主题？

Question

I want to export rxjs Subject with some pre-defined behavior (via pipe() ).

eg I want to export a subject that do console.log on each new value:

export const subj$ = new Subject()
  .pipe(
    tap(() => console.log('updated')
  )

This works, and I'm able to subscribe() to subj$ .

The problem is that this way it's impossible to do subj$.next('foo') .

Of course I can export two variables for subscribe() and for next() , but that's supper silly

Answer 1

Actually you cannot do this. Because pipe converts Subject to Observable and this record is similar to this: new Subject().asObservable() .

But, you can create your own Subject , for example from source ( https://github.com/ReactiveX/rxjs/blob/master/src/internal/BehaviorSubject.ts ). And make any function to invoke inside.