map

Namespace: FsToolkit.ErrorHandling

map applies a transformation to the value inside an AsyncValidation if it represents a successful result (Ok). It allows you to perform a computation on the value while preserving the success/error status of the original AsyncValidation. If the original AsyncValidation is an Error, map does nothing and returns the same Error unchanged.

Function Signature

('okInput -> 'okOutput) -> AsyncValidation<'okInput, 'error> -> AsyncValidation<'okOutput, 'error>

Examples

Take the following functions for example

// string -> int
let remainingCharacters (prompt: string) =
    280 - prompt.Length

Example 1

let validation =
    AsyncValidation.ok "foo" // AsyncValidation<string, string>
    |> AsyncValidation.map remainingCharacters // AsyncValidation<int, string>

// async { Ok 277 }

Example 2

let result =
    AsyncValidation.error "bad things happened" // AsyncValidation<string, string>
    |> AsyncValidation.map remainingCharacters // AsyncValidation<int, string>

// async { Error ["bad things happened"] }