apply
Namespace:
FsToolkit.ErrorHandling
apply
combines two Result values and returns a new Result value. If both Result values are Ok, it applies the function from the first Result to the value from the second Result, producing a new Result type. If either Result is an Error, the apply function propagates the error by returning the corresponding Error value.Result<('okInput -> 'okOutput), 'error> -> Result<'okInput, 'error>
-> Result<'okOutput, 'error>
Note: The
apply
function is most useful in its infix operator form <*>
when using it over a multi-parameter function. Examples of this is shown in the documentation for this operator. The example below is a bit artificial since map
is arguably better.// Tweet -> int
let remainingCharacters (tweet : Tweet) =
280 - tweet.Value.Length
If we want a function that takes a plain string instead, we can achieve it using the
apply
function:// string -> Result<int,string>
let remainingCharactersStr (tweetStr : string) =
Tweet.TryCreate tweet
|> Result.apply (Ok remainingCharacters)
But as mentioned, using the
map
function is simpler in this case:// string -> Result<int,string>
let remainingCharactersStr (tweetStr : string) =
Tweet.TryCreate tweet
|> Result.map remainingCharacters
Last modified 2mo ago