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Add StreamMessage.flatMap() #3966

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sleeplesslord opened this issue Dec 2, 2021 · 3 comments · Fixed by #4227
Closed

Add StreamMessage.flatMap() #3966

sleeplesslord opened this issue Dec 2, 2021 · 3 comments · Fixed by #4227
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new feature sprint Issues for OSS Sprint participants

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@sleeplesslord
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sleeplesslord commented Dec 2, 2021 •
edited

StreamMessage has map which allows mapping the values in a stream with a function. It doesn't currently have flatMap so it's difficult to work with a function that itself returns a StreamMessage, for example when chaining multiple operations.

interface StreamMessage<T> {
    StreamMessage<U> flatMap(Function<T, StreamMessage<U>> function);
}
@sleeplesslord
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I'll work on this and make a PR when it's ready 😄

@ikhoon
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ikhoon commented Dec 2, 2021

JFYI, there is a difference in subscription between concatMap and flatMap.
ConcatArrayStreamMessage could be a good example for the flatMap operation.

@trustin
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trustin commented Mar 28, 2022

Looking forward to this, @sleeplesslord! 🙇

@sleeplesslord sleeplesslord mentioned this issue Apr 25, 2022
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@trustin trustin added the sprint Issues for OSS Sprint participants label Feb 16, 2023
ikhoon added a commit that referenced this issue Apr 9, 2024
@sleeplesslord @jrhee17
@minwoox @ikhoon
Add flatMap method for collapsing streams into one (#4227)
211a9e5 
Motivation:
`StreamMessage` has `map`, but it is inconvenient to use it when the
mapping function itself returns a `StreamMessage`. This PR adds
`flatMap` which allows applying a function that returns a
`StreamMessage` without ending up with nested `StreamMessage`s.

Modifications:
- Add `FlatMapStreamMessage`, which uses a function that returns a
`StreamMessage` to modify the stream.
- Add `StreamMessage.flatMap()` to allow easily creating a
`FlatMapStreamMessage` from an existing stream.

Result:
- Closes #3966 
- You can now use `StreamMessage.flatMap` to modify a stream using a
function that returns a `StreamMessage`.

---------

Co-authored-by: jrhee17 <guins_j@guins.org>
Co-authored-by: minwoox <songmw725@gmail.com>
Co-authored-by: Ikhun Um <ih.pert@gmail.com>
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Add flatMap method for collapsing streams into one sleeplesslord/armeria
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@trustin @ikhoon @sleeplesslord