Comment by tumultco | Hacker News Reader

Comment by tumultco | Hacker News Reader

Nice mustache! Here's some other Foundation classes/methods which are very useful but lesser known:

NSCountedSet - and NSMutableSet that keeps counts of objects added

NSValueTransformer - More of a design pattern for generically converting objects

NSArgumentDomain in NSUserDefaults - command line arguments of -key value become user defaults

NSXMLNode nodesForXPath:error:/objectsForXQuery:error: - run XPath or XQuery against XML... even better, subclass NSXMLNode and then use XPath and XQuery on any hierarchical data you have

NSObject's performSelectorOnMainThread:withObject:waitUntilDone: - use NO for waitUntilDone and the method will be called at the end of the event loop (I've seen many people use the afterDelay variant instead)

NSNotificationQueue - use NSNotificationCoalescingOnName to batch up NSNotifications to send a single one at the end of the event loop, though there's lots of gotchyas for using it correctly

NSOrthography - Okay, even I didn't know about this before re-glancing at the foundation reference :)

It's interesting how much of the Foundation consists of patterns for overcoming the awkwardness of Objective-C.

For example, in most modern languages, NSCountedSet is crazy trivial; you just use a hash of numbers. But since Obj-C doesn't have autoboxing (well, it kinda sorta does nowadays, but anyway), having a built in implementation is nice.

NSValueTransformer is a similar workaround for a lack of language features, which will look particularly alien if you're used to languages with proper closures and autoboxing. They are a boilerplate nightmare, and Apple would have done well to provide some simple implementation that could be controlled from the interface builder years ago (based on JavaScript expressions, for example).

Anyway, a fun exercise with NSValueTransformers is to build a subclass for chaining them together (bonus points for automatic reversing), and then a subclass of simple primitive operations that you can compose into more complex transformers. This can actually be pretty useful if, for example, you have a number of log-scale sliders and text fields that require slightly different transformation parameters.

I think my above comment may have come across as unnecessarily harsh against Objective-C. I like Obj-C and I was actually trying to make a broader point: you can often learn a lot about a language's weaknesses and quirks by digging into its standard library.

Oh my god, NSValueTransformer. Why has this not been in my life the past two weeks. Same goes for performSelectorOnMainThread. Thankyou.

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