MetaMurph: Writing about Cocoa and iPhone Development

Even though hand crafting source lists are a lost art on Leopard (since the look is now offered natively in AppKit), for cross-developed applications or other styling needs, I’d to demonstrate a safe and sturdy technique for custom drawn NSTableView row highlights.

One seemingly always overlooked fact about NSTableView subclassing is that custom row highlighting can be achieved solely by overriding public, documented methods on 10.4 and above. A decent number of NSTableView subclasses I’ve come across, mainly source list implementations, accomplish customized row highlighting by stepping in the way of the superclass’s normal highlight drawing process by overriding a private and undocumented method called “-_highlightColorForCell.”

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Crafting software is more than just mastering the syntax of any given language – the overall architecture, relationships and interaction among an application’s source code weigh in heavily to define true engineering elegance. A winning design is often harder to achieve than superior syntax, since the solutions are not as clear cut and mistakes are not immediately obvious. No compiler can warn us of poor architectural and design decisions, we instead realize such problems maintaining our code in the future. Thankfully, design principles and patterns exist to help us write elegant software.

One design template relied upon heavily by Cocoa’s Foundation framework is the class cluster, which is implemented in a manner consistent with the Abstract Factory design pattern. I’d like to explain how you’d actually go about rolling one of these yourself, and also touch on some of the motivating factors for introducing such a pattern into your own application. Later, I’ll relate to a real-world example of a class-cluster I designed for use in Camino to support the flexible parsing of search engine plugins.

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