(A quick note: This blog post was drafted with the help of an AI assistant based on the official Uniface 10.4 documentation to ensure clarity and provide helpful examples.)

Ever found yourself writing Uniface ProcScript and wondering, “Does this compiled component even exist before I try to call it?” 🤔 We’ve all been there. Trying to access a resource that isn’t there can lead to annoying runtime errors. Luckily, Uniface provides a handy tool to prevent this: the $ude("exist") function.

This guide will simply break down what it is, how to use it, and why it’s a great tool for your developer toolbox. 🛠️

What is $ude(“exist”)?

In short, $ude("exist") is a built-in function that checks if a specific Uniface resource is available. Think of it as a little detective 🕵️‍♀️ that you can send out to see if a file or object is ready and waiting. You can use it to check for three main types of things:

• Compiled runtime objects (like forms, services, or messages)
• Symbol tables (used by the compiler)
• ProcScript listings (the text output of your scripts)

How to Use It: The Syntax

The basic structure of the function looks like this:

vResult = $ude("exist", "Type;ResourceType", "ResourceName", "", "OptionList")

Let’s break that down:

• Type: Tells Uniface what you’re looking for. The most common one is resources_output for compiled objects.
• ResourceType: Gets more specific. Are you looking for a component, a form, a service, or maybe just a message?
• ResourceName: The actual name of the item you’re checking for, like “MY_COMPONENT” or “ERROR_MSG_001”.
• OptionList: This is super important! If you’re looking for a global object, you must specify its library here (e.g., library=MY_LIB). For resources like messages or menus, you often need to add the language, too (e.g., language=USA).

Let’s See an Example! 💻

Imagine you have a library named MyLib and you want to check if a compiled message named generror exists for the French language (fr).

Your ProcScript would look like this:

variables
string vResult
endvariables

vResult = $ude("exist", "resources_output;message", "generror", "", "library=MyLib;language=fr")

if (vResult = "1")
putmess "The 'generror' message exists for French. C'est bon!"
else
putmess "Oops, the 'generror' message for French is missing."
endif

Understanding the Results

The function is very straightforward in what it gives back:

• “1”: Success! The object exists. ✅
• “0”: Nope. The object was not found. ❌

If something else goes wrong (like a typo in your parameters), $status will return a negative number, and you can check $procerror for more details.

Why Is This Useful?

Using $ude("exist") makes your applications more robust and stable. Here are a few ideas:

• Avoid Errors: Check if a dynamic component exists before you try to activate it.
• Deployment Scripts: Write a script to verify that all necessary components and messages were successfully compiled and deployed.
• Fallback Logic: If a language-specific resource doesn’t exist, you can gracefully fall back to a default language (like English) instead of crashing.

So next time you’re working with dynamic resources, give $ude("exist") a try. It’s a simple but powerful function that can save you from future headaches. Happy coding! 😄