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Feedback from Remote in piglet errors?
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I have a simple piglet form which contains some validation. When the piglet is run, I send the data fetched from it to a remote call. This remote call will either success, which will trigger a redirect to a different page, or a failure, which is basically just a string message of the error. I am looking to find a way to display this string within the form. How would I do this?

.

Alright, I managed to do it in the end. Here's how I did it basically.

I created an extra input and made it's stream available.

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let feedback, feedbackStream =
    Piglet.Yield ""
    |> fun feedback -> feedback, feedback.Stream

With the stream now available, within the Piglet.run I could do something like this

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Start (fun () -> Remoting.Call data) (fun result ->
    feedbackStream.Trigger (Result.Success result)
)

Within the render function, I did something like this

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Div [] |> Controls.ShowString feedback (fun x -> string x)

I don't know if this is the most optimal way but it's working for me so far.

By on 3/7/2015 12:20 PM ()

What you probably want to look at here is the Piglet.MapAsync family of functions, and more precisely Piglet.MapToAsyncResult. For example, if you have a RemoteFunction that returns an Async<option<string>> (None on success, Some "error message" otherwise) then you can do:

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yourPiglet
|> Piglet.MapToAsyncResult (fun x ->
    async {
        let! result = RemoteFunction x
        return
        	match result with
            | None -> Result.Success x
            | Some message -> Result.Failwith message
    }
)
|> Piglet.TransmitReader
|> Piglet.Render (fun yourPigletStreams result ->
    Div [
        // Render your piglet...
        Div [] |> Controls.ShowErrors result (fun messages ->
            Seq.map Text messages)
    ]
)

Notice also the use of Piglet.TransmitReader to pass the final value as a read-only stream to the render function. This is more composable that extracting the stream explicitly like you did.

By on 3/8/2015 3:26 AM ()

Indeed, that looks very clean. I will refactor my code around that. Thank you very much.

By on 3/8/2015 9:35 AM ()

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