Error handling refers to the response and recovery procedures from error conditions present in a software application. It is the process comprised of anticipation, detection and resolution of application errors, programming errors or communication errors.
If you're solving complex problems in ObjectScript, you probably have a lot of code that works with %Status values. If you have interacted with persistent classes from an object perspective (%Save, %OpenId, etc.), you have almost certainly seen them. A %Status provides a wrapper around a localizable error message in InterSystems' platforms. An OK status ($$$OK) is just equal to 1, whereas a bad status ($$$ERROR(errorcode,arguments...)) is represented as a 0 followed by a space followed by a $ListBuild list with structured information about the error. $System.Status (see class reference) provides several handy APIs for working with %Status values; the class reference is helpful and I won't bother duplicating it here. There have been a few other useful articles/questions on the topic as well (see links at the end). My focus in this article will be on a few debugging tricks techniques rather than coding best practices (again, if you're looking for those, see links at the end).
Standard error logs in IRIS / Caché / Ensemble are written global ^ERRORS. As this piece dates back some decades back to previous millennium its structure is far from the typical SQL storage structures.
Error management on InterSystems languages has been evolving along time. Next, we will show the different implementations and why you should use the TRY/THROW/CATCH mechanism.
A unit of ObjectScript code (a ClassMethod, say) may produce a variety of unexpected side effects by interacting with parts of the system outside of its own scope and not properly cleaning up. As a non-exhaustive list, these include:
ObjectScript has at least three ways of handling errors (status codes, exceptions, SQLCODE, etc.). Most of the system code uses statuses but exceptions are easier to handle for a number of reasons. Working with legacy code you spend some time translating between the different techniques. I use these snippets a lot for reference. Hopefully they're useful to others as well.
Hello again! Welcome to the Part 2 - Handling payloads!
If you're new to this series, I'd recommend you to check out the Part 1 - Core concepts. You'll need a basic understanding about how Frontier works before continuing with the Part 2.
A beginner’s guide to Exception Handling in RESTful web services. The article gives an example how the various error conditions during processing a service request can be handled.
We expect our client – server communication working in a flawless operational condition, running error free software. But we are prepared to handle exceptions. Are we? So far in the examples of the previous sessions were not. We did not care about exceptions. The result? In any error incident it took ages to figure out what the problem is and more importantly how to fix it.
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