codesomnia

Preface

In my last post I gave two possible approaches and a preview of my final solution for handling errors in IResults. The syntax for my final solution was

yield return new ProcessDataResult()
		.Rescue().With(coroutine: IORescue)
		.Rescue().With(coroutine: GeneralRescue);

This means that

• whenever the result completes with an error of type IOException, the IORescue coroutine is executed
• whenever the result completes with any other error, the GeneralRescue coroutine is executed

So the behaviour of the Rescue is similar to a try/catch block

try {}
catch (IOException e) { //IORescue }
catch (Exception e) { //GeneralRescue }

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The Problem

One of Caliburn.Micro’s nicest feature is, hands down, the concept of Actions. In that concept the IResult plays an important role, especially when using Coroutines. If you don’t know about them, you should definately read up on them here first.

So, let’s assume we are executing a Coroutine which first shows a loading screen to the user, then starts processing a lot of data and finally hides the loading screen once the processing is finished. Since the processing is also likely to fail for whatever reason we want to handle the error by executing a Rescue Coroutine.

public IEnumerable ProcessData()
{
	yield return new BusyResult("Processing...");

	yield return new ProcessDataResult();

	yield return new NotBusyResult();
}

The implementation of those results is irrelevant since we want to have a look at how we can handle the error during the processing in a nice (reusable) way.

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