In addition to the frameworks provided by Apple, several third-party objective frameworks are available. One of the most notable is the collection of frameworks from The Omni Group. Omni makes not only the same frameworks developers use in their applications, but also the source code for the frameworks.
Omni provides the following frameworks, whose source code can be downloaded from Omni's developer web site (http://www.omnigroup.com/developer/sourcecode):
This framework provides several low-level classes that provide allocation and initialization debugging aids, classes that aid interaction with the Objective-C runtime, and an exception handling mechanism that is an alternative to the standard one provided in Cocoa.
This framework provides several extensions to Cocoa's Foundation framework, including classes that handle strings, scanning, and regular expressions.
This framework is an Objective-C wrapper to the networking libraries that already exist in Mac OS X. OmniNetworking supports major networking protocols such as Multicast, TCP, and UDP.
This framework provides lots of neat controls, such as a calendar and chasing arrows, as well as larger application components such as a skeletal preferences system and Find panel.
The Omni Web Framework is the base architecture for OmniWeb that handles all content retrieval and parsing, and other functions related to Internet application development. Omni says: "If OmniFoundation is the Objective-C programmer's Swiss Army Knife, then OWF is their double barrel, rotary laser cannon."
This framework handles HTML parsing and is also used in OmniWeb.
These frameworks provide no documentation. However, with the source code available, learning how to use them should be fun.
Another notable framework is the MiscKit, maintained by the Object Foundation. The framework contains a plethora of miscellany. Undoubtedly, many of you will find the offerings of the MiscKit useful and interesting. Information about MiscKit, as well as resources and the actual framework, is available at http://www.misckit.com.
In addition to these larger frameworks, many smaller collections of classes are constantly growing and improving. The Cocoa development community is outputting several free, open source classes. The Softtrak software database, available on Stepwise's site (http://www.stepwise.com), maintains information about the third-party frameworks available for Cocoa.