I'm doing this in one of my route guards...
canActivate(route: ActivatedRouteSnapshot, state: RouterStateSnapshot): Observable<boolean> {
// go through each check sequentially, stop process if one does throwError
return of(true).pipe( // Is there a limit to operators in a pipe???
switchMap(() => of(true)), // simplified for this post...usually call a function that returns
switchMap(() => of(true)),
switchMap(() => of(true)),
switchMap(() => of(true)),
switchMap(() => of(true)),
switchMap(() => of(true)),
switchMap(() => of(true)),
switchMap(() => of(true)),
// if any function returns throwError, we skip other checks
catchError(() => of(false))
);
}
I'm running into an error. If there is one more switchMap added to the list, VSCode tells me... "Type 'Observable<{}>' is not assignable to type 'Observable'. Type '{}' is not assignable to type 'boolean'.ts(2322)"
Can somebody explain to me why that's the case? I can't figure it out and find related issues.
This is pretty well explained in this github issue.
The gist of it is that only 9 operators are supported - any more and it will fall back to type Observable<{}> since they have to manually type everything up to 9 operators.
Use multiple pipes (maintains typesafety after the 9nth entry)
If you still want to maintain typesafety but add more than 9 operators, just call the pipe function again.
source$
.pipe(
tap(() => {}),
tap(() => {}),
tap(() => {}),
tap(() => {}),
tap(() => {}),
tap(() => {}),
tap(() => {}),
tap(() => {}),
tap(() => {})
)
.pipe(
// Add the next operators after the 9nth here
tap(() => {})
)
Manually assert the resulting type
Alternatively, you can add a manual type assertion at the end. Beware though: After the 9nth operator, the type will be infered as Observable<{}>, effectively losing typesafety.
const source$:Observable<boolean> = of(true)
.pipe(
tap(() => {}),
tap(() => {}),
tap(() => {}),
tap(() => {}),
tap(() => {}),
tap(() => {}),
tap(() => {}),
tap(() => {}),
tap(() => {}),
// Typesafety is lost here
tap(() => {}),
tap(() => {}),
// Manually assert the type at the end
// Beware that the compiler will allow pretty much anything here,
// so "as Observable<string>" would work, even though it'd be wrong.
) as Observable<boolean>;