Bringing back Method Chaining

[MichaelSchneeberger]

#743 brough back Method Chaining for Observables - a feature presented in the early versions of RxPY.

Out of curiousity, @dbrattli: What advantages does method chaining provide alongside the function style pipe-style approach?

[dbrattli]

Hey, it's just an alternative way of writing the queries. E.g:

(
    rx.of(1, 2, 3, 4, 5)
    .map(lambda x: x * 2)
    .filter(lambda x: x > 5)
    .take(3)
    .subscribe(print)
)

Personallly I have missed this way of writing Rx and wanted to bring it back. For the expression library I have enabled both syntaxes from the start so you can choose. There is one advantage, and that is you can easliy discover the method by tab expansion e.g:

>>> from reactivex import of
>>> xs = of(1,2,3)
>>> xs.flat_map
xs.flat_map(          xs.flat_map_indexed(  xs.flat_map_latest(         

E.g for F# you can use fluent additions like https://fsprojects.github.io/FSharp.Core.Fluent/

[dbrattli]

The advantage of the pipe syntax is that you are free to add your own operators without the need to have them added to the library. This library is already very large and we don't want to keep adding new operators since it makes it harder to maintain 😅