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atomkirk/Copy if Copyable.md

Last active December 17, 2015 23:39
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Copying + mutable = @Property (copy)
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Copy if Copyable.md

I've been told about this, but it's never bitten me, until today. So, get in the habit:

http://stackoverflow.com/questions/387959/nsstring-property-copy-or-retain

He says immutable and I'm not sure I understand why, but it's clear why you would do this with mutable. UPDATE: he says immutable, implying mutable too, because it's entirely possible to assign an immutable version of an object to a property specified as mutable, so it's not safe to assume that just because the property is NSArray doesn't mean it isn't a mutable array and some statement somewhere isn't changing it's content's behind your back.

One interesting thing to note: if you assign an immutable NSArray to a @property (copy, nonatomic) NSArray *array it will actually retain it, not copy it. So it's is smart enough to just retain rather than copy it when it really is immutable, saving an allocation.

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