30 lines
795 B
Markdown
30 lines
795 B
Markdown
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# Flow.flattenOptional
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Collect the value of `Optional` from all the elements passing through this flow , empty `Optional` is filtered out.
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@ref[Simple operators](../index.md#simple-operators)
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## Signature
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@apidoc[Flow.flattenOptional](Flow$) { java="#flattenOptional(akka.stream.javadsl.Flow)" }
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## Description
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Streams the elements through the given future flow once it successfully completes.
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If the future fails the stream is failed.
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## Reactive Streams semantics
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@@@div { .callout }
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**Emits when** the current @javadoc[Optional](java.util.Optional)'s value is present.
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**Backpressures when** the value of the current @javadoc[Optional](java.util.Optional) is present and downstream backpressures.
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**Completes when** upstream completes.
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**Cancels when** downstream cancels.
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@@@
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