If you are interested to contribute to Étoilé directly or by writing your own applications, I have compiled below some resources to learn GNUstep programming…
The best resource for Objective-C development with Cocoa/GNUstep frameworks is Apple documentation in my opinion. Cocoa documentation is now excellent, but don't forget GNUstep isn't always in sync with Cocoa and Carbon stuff isn't available on GNUstep platforms.
To begin the best is probably to read the following Apple guide: Cocoa Fundamentals.
On GNUstep website, visit Developer documentation area. From this documentation, you should read gnustep-make documentation. Take note it isn't really exhaustive and doesn't cover the new stuff brought by latest release 2.0. Base Programming Manual can be worth to read. It details a bit some GNUstep specific extensions like Documentation system, logging etc. and includes a very good overview of Distributed Objects with real examples.
GNUstep API references:
- Foundation Additions… This is the place where you can find documentation on XML support and Runtime utility functions.
- Foundation Tools… Important place where GNUstep Documentation system (aka GSDoc) with the related tool autogsdoc is explained.
Cocoa Dev Central is a good place to start with plenty of nice tutorials too.
Here are other very good guides you can read to dig into GNUstep development:
- Application Architecture
- Memory Management
- Document based Application
- Event Handling
- Coding Guidelines
- Objective-C Language
If you are interested by books, check: