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    <p>Regardless of your memory management system, tying expensive resources (e.g. files &amp; sockets, images, views, large memory allocations, etc) to object lifetimes is risky. Even if you're manually retaining &amp; releasing, you might unwittingly retain an object somewhere and forget about it (or otherwise delay its release unnecessarily). ARC makes it even more likely that these things will happen, since it's much less apparent where the retains come from, and when the corresponding releases take effect. And of course GC makes it all completely indefinite.</p> <p>Generally for expensive and/or limited resources you should try to follow a sole-ownership pattern. Yes, you can still retain/release as normal to prevent premature deallocation, but the dominant owner should be well defined and responsible for clearing out the object when it's done - e.g. calling invalidate, or close, or whatever is appropriate. This makes perfect sense in a lot of the common cases - you generally know when you're done with a file or a socket, for example, so even if they happen to be encapsulated inside some wrapper class, you should just close them explicitly.</p> <p>In some cases this can also help find bugs that would otherwise remain hidden, or be hard to track down. For example, if your file wrapper class raises an exception when read or write are called after the file is closed, you'll soon catch those cases. Whereas if you didn't close the file when you <em>thought</em> you were done with it, the reads and writes would just happen as usual and you might not notice that your file has unexpected data in it.</p> <p>You can also use the same principles to break retain cycles.</p>
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    1. USWade Tregaskis
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      1. VTUpMod
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