What is the cleanest way work with a chain of `Opt...

# announcements

[Michael]

What is the cleanest way work with a chain of Optionals when you need to hang on to intermediate values? (“Promise Hell” in JavaScript) Sample:

return receiptRepository.findOne(receiptId)
    .map { lineRepository.findOne(it, lineId) }
    .map { lineRepository.update( /* need receipt here */, it, updatedLine) }
    .map { ResponseEntity(it, HttpStatus.OK ) }
    .orElse { ResponseEntity(HttpStatus.NOT_FOUND) }

[Andreas Sinz]

.map { lineRepository.findOne(it, lineId) to it }?

[Andreas Sinz]

or

.map { 
    val line = lineRepository.findOne(it, lineId)
    lineRepository.update(it, line, updatedLine)
}

[Michael]

Busy missing the trees for the forest. THank you!

[marstran]

This is where for-comprehension syntax would be nice. Like in this Scala'ish code:

val response = for {
  receipt <- receiptRepository.findOne(receiptId)
  line <- lineRepository,findOne(receipt, lineId)
  lineUpdate <- lineRepository.update(receipt, line, updatedLine)
} yield ResponseEntity(lineUpdate, HttpStatus.OK)

return response.orElse { ResponseEntity(HttpStatus.NOT_FOUND) }

[Michael]

yeah, that’d be nice!

[gildor]

#C5UPMM0A0 has bindings that allow to write such code much easier