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TraverseFilter
/arrow/typeclasses/traversefilter/

TraverseFilter

TraverseFilter is helpful when you want to combine Traverse and FunctorFilter as one combined operation. This doc focuses on the methods provided by the typeclass.

Main Combinators

TraverseFilter includes all combinators present in [Traverse]({{ '/arrow/typeclasses/traverse/' | relative_url }}) and [FunctorFilter]({{ '/arrow/typeclasses/functorfilter/' | relative_url }}).

Kind<F, A>#traverseFilter

Returns F<B> in G context by applying AP on a selector function f, which returns Option of B in G context.

Kind<F, A>#filterA

Returns F<A> in G context by applying GA on a selector function f in G context.

Kind<F, A>#traverseFilterIsInstance

Filter out instances of a specific type and traverse a context.

Laws

Arrow provides TraverseFilterLaws{:target="_blank"} in the form of test cases for internal verification of lawful instances and third party apps creating their own TraverseFilter instances.

Creating your own TraverseFilter instances

Arrow already provides TraverseFilter instances for most common datatypes both in Arrow and the Kotlin stdlib. Oftentimes, you may find the need to provide your own for unsupported datatypes.

See [Deriving and creating custom typeclass]({{ '/patterns/glossary' | relative_url }})