orElse.md

Validation.orElse / Validation.orElseWith

Namespace: FsToolkit.ErrorHandling

orElse

orElse returns the original Validation if it is Ok, otherwise returns the provided alternative Validation.

Function Signature

Validation<'ok, 'errorOutput> -> Validation<'ok, 'errorInput> -> Validation<'ok, 'errorOutput>

Examples

Example 1

let result =
    Validation.ok "First"
    |> Validation.orElse (Validation.ok "Second")

// Ok "First"

Example 2

let result =
    Validation.error "First"
    |> Validation.orElse (Validation.ok "Second")

// Ok "Second"

Example 3

let result =
    Validation.error "First"
    |> Validation.orElse (Validation.error "Second")

// Error ["Second"]

---

orElseWith

orElseWith returns the original Validation if it is Ok, otherwise calls the given function with the error list and returns its result.

Function Signature

('errorInput list -> Validation<'ok, 'errorOutput>) -> Validation<'ok, 'errorInput> -> Validation<'ok, 'errorOutput>

Examples

Example 1

let result =
    Validation.ok "First"
    |> Validation.orElseWith (fun _ -> Validation.ok "Second")

// Ok "First"

Example 2

let result =
    Validation.error "First"
    |> Validation.orElseWith (fun _ -> Validation.ok "Second")

// Ok "Second"

Example 3

let result =
    Validation.error "First"
    |> Validation.orElseWith (fun errors ->
        Validation.error $"Recovered from: %A{errors}")

// Error ["Recovered from: [\"First\"]"]