traverseTaskResult

Option.traverseTaskResult

Namespace: FsToolkit.ErrorHandling

Function Signature:

('a -> Task<Result<'b,'c>>) -> 'a option -> Task<Result<'b option, 'c>>

Note that traverse is the same as map >> sequence. See also Option.sequenceTaskResult.

See also Scott Wlaschin's Understanding traverse and sequence.

Examples

Example 1

Say we have a function to get a number from a database (asynchronously), and multiply our input by that number if it's found:

let tryMultiplyWithDatabaseValue: float -> Task<Result<float, string>> = // ...

If we start with an optional value, then we could map this function using Option.traverseTaskResult as follows:

let input = Some 1.234

input // float option
|> Option.traverseTaskResult tryMultiplyWithDatabaseValue // Task<Result<float option, string>>

If we combine this with the TaskResult computation expression, we could directly let! the output:

taskResult {
    let input = Some 1.234

    let! output = // float option
        input // float option
        |> Option.traverseTaskResult tryMultiplyWithDatabaseValue // Task<Result<float option, string>>
}