do not allow multiple instances of the GUI Apps

[mbreiser]

strange behavior occurs when more than one instance of any of the 3 apps. when app opens -- check to see if one already open and post warning (and don't open)

[taylorlm88]

Which GUI apps are you referring to?

[mbreiser]

Fixed: Singleton Pattern Implementation

Problem

Constructor logic was backwards - checked for existing instances AFTER creating components, so both old and new instances were found in the search.

Solution

Moved singleton check BEFORE createComponents() call. When existing instance detected:

1. Brings existing app to front
2. Shows alert dialog: "[App] is already open. Only one instance is allowed."
3. Throws error: [AppName]:SingletonViolation

Implementation

All three apps now implement singleton pattern correctly:

• PatternGeneratorApp
• PatternPreviewerApp
• PatternCombinerApp

Testing

Created test suite: tests/test_singleton_pattern.m

All tests pass:

=== Summary ===
Passed: 3 / 3
All tests PASSED!

Documentation

Added mandatory singleton testing requirements to CLAUDE.md for future constructor modifications.

Ready to close.