iphone - Hidden features of Objective-C -

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objective-c getting wider use due use apple mac os x , iphone development. of favourite "hidden" features of objective-c language?

  • one feature per answer.
  • give example , short description of feature, not link documentation.
  • label feature using title first line.

method swizzling

basically, @ runtime can swap out 1 implementation of method another.

here explanation code.

one clever use case lazy loading of shared resource: implement sharedfoo method acquiring lock, creating foo if needed, getting address, releasing lock, returning foo. ensures foo created once, every subsequent access wastes time lock isn't needed more.

with method swizzling, can same before, except once foo has been created, use swizzling swap out initial implementation of sharedfoo second 1 no checks , returns foo know has been created!

of course, method swizzling can trouble, , there may situations above example bad idea, hey... that's why it's hidden feature.


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