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.
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."
