FsToolkit.ErrorHandling
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  • FsToolkit.ErrorHandling
    • Result
      • apply
      • bind
      • check
      • Computation Expression
      • either Functions
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      • Transforms
        • ofNull
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    • ResultOption
      • apply
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    • AsyncResult
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        • ofAsync
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    • AsyncResultOption
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        • ofAsyncOption
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      • error
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        • traverseTaskResultM
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        • ofAsync
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      • apply
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      • error
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      • Operators
    • Validation
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      • error
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      • mapError
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      • Operators
      • zip
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        • ofChoice
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    • AsyncValidation
      • apply
      • Computation Expression
      • error
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      • mapError
      • mapErrors
      • Operators
      • zip
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        • ofChoice
        • ofResult
    • TaskValidation
      • apply
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      • error
      • map
      • map2
      • map3
      • mapError
      • mapErrors
      • Operators
      • zip
      • Transforms
        • ofChoice
        • ofResult
  • FsToolkit.ErrorHandling.AsyncSeq
    • AsyncSeq
      • Computation Expression
  • FsToolkit.ErrorHandling.IcedTasks
    • CancellableTaskOption
      • apply
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      • getCancellationToken
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      • zip
      • parallelZip
    • CancellableTaskValidation
      • apply
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      • error
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      • map
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      • mapError
      • mapErrors
      • Operators
      • zip
      • parallelZip
      • Transforms
        • ofChoice
        • ofResult
  • FsToolkit.ErrorHandling.JobResult
    • Job
      • apply
      • map2
      • map3
      • singleton
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    • JobOption
      • apply
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      • ce
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      • error
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      • zip
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        • traverseJobResultM
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        • traverseJobResultA
        • sequenceJobResultA
      • Transforms
        • ofAsync
        • ofJob
        • ofResult
        • fromTask
        • fromUnitTask
    • JobResultOption
      • apply
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      • Computation Expression
      • ignore
      • map
      • map2
      • map3
  • General Docs
    • Bind Mappings
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  • Function Signature
  • Examples
  • Example 1
  • Example 2
  1. FsToolkit.ErrorHandling
  2. AsyncResult

check

Namespace: FsToolkit.ErrorHandling

The intent of check is to allow an Ok result value to be validated.

check takes a validation function of the form 'ok -> Async<Result<unit, 'error>> and a result of the form Async<Result<'ok, 'error>>.

If the async-wrapped result is Ok x then the validation function is applied, and if the validation function returns an error, this new async-wrapped error is returned. Otherwise, the original async-wrapped Ok x result is returned. If the original async-wrapped result is an Error, the original async-wrapped result is returned.

Function Signature

('ok -> Async<Result<unit,'error>>) -> Async<Result<'ok,'error>> -> Async<Result<'ok,'error>>

Examples

Given the following function that returns true for the id 123

checkEnabled : int -> Async<bool>

Example 1

AsyncResult.ok (
    {|
        PolicyId = 123
        AccessPolicyName = "UserCanAccessResource"
    |}

)
|> AsyncResult.check (fun policy ->
    asyncResult {
        let! isEnabled = checkEnabled policy.PolicyId

        return
            if not isEnabled then
                Error(
                    $"The policy {policy.AccessPolicyName} cannot be used because its disabled."
                )
            else
                Ok()

    }
)
// AsyncResult.Ok {| AccessPolicyName = "UserCanAccessResource"; IsEnabled = true; |}

Example 2

AsyncResult.ok (
    {|
        PolicyId = 456
        AccessPolicyName = "UserCanAccessResource"
    |}

)
|> AsyncResult.check (fun policy ->
    asyncResult {
        let! isEnabled = checkEnabled policy.PolicyId

        return
            if not isEnabled then
                Error(
                    $"The policy {policy.AccessPolicyName} cannot be used because its disabled."
                )
            else
                Ok()

    }
)

// AsyncResult.Error "The policy UserCanAccessResource cannot be used because its disabled."
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Last updated 4 months ago