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Promise.then() is difficult to use with lambdas

See original GitHub issue

Currently Promise.then takes 3 different types of inputs: DoneCallback, DoneFilter, and DonePipe. This forces explicit casts when using lambda expressions. It would be better if this method were to be split in 3 variants, such as

then(DoneCallback cbk)
thenFilter(DoneFilter fltr)
thenPipe(DonePipe pipe)

Issue Analytics

State:
Created 6 years ago
Comments:5 (5 by maintainers)

Top GitHub Comments

1reaction

sclassencommented, Oct 1, 2018

yes. DoneFilter returns D_OUT which is then wrapped in a new Promise<D_OUT, F, P>, where as DonePipe returns Promise<D_OUT, F_OUT, P_OUT> So if we would apply the DonePipe as a map() we would get Promise<Promise<D_OUT, F_OUT, P_OUT>, F, P> Because this is just complicated and does not add any value the pipe operation unwraps the inner promise. The same does the flatMap() on streams. it unwraps a stream in a stream -> it flattens the generic…

Does this explanation help?

0reactions

aalmiraycommented, Oct 1, 2018

I get s/filter/map/ but isn’t pipe a variation of mapas well?