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Comment by natesm | Hacker News Reader

What's the advantage of implementing map/filter as property accessors of a wrapper object instead of just doing:

    NSArray* map(id<NSFastEnumeration> enumerable, id(^)(id object) block);

Obviously, you'd still want to have a prefix of some sort for namespacing.

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In the case of NSDictionary, Underscore.m's map iterates over objects and keys. Fast Enumeration only iterates over the dictionary's keys, when you probably want the value or both.

But I agree, supporting any class that implements NSFastEnumeration would be nice to have.

You may already know this, but you can also enumerate over NSDictionary entries using enumerateKeysAndObjectsUsingBlock: [1] and enumerateKeysAndObjectsWithOptions:usingBlock: [2].

The latter giving you the ability to enumerate in reverse order or spread the enumeration across multiple cores using Grand Central Dispatch.

[1] https://developer.apple.com/library/mac/documentation/Cocoa/...: [2] https://developer.apple.com/library/mac/documentation/Cocoa/...:

It's exactly what's used internally :)

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