# build_flatMap(_:_:) ``` static func build_flatMap(_ wrapped: LHS, _ builder: (PredicateExpressions.Variable) -> RHS) -> PredicateExpressions.OptionalFlatMap where LHS : PredicateExpression, RHS : PredicateExpression, LHS.Output == Wrapped?, RHS.Output == Result? ``` --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)