On 22 May 2015, at 7:49 AM, Alex Zavatone <[email protected]> wrote:
> @property (nonatomic, strong) NSString *thing;
>
Another chore in porting this code: The retention attribute should be copy, not
strong.
If you needed to track changes in the string, you'd use strong, but NSStrings
don’t mutate; NSMutableStrings do.
If you do assign a mutable string into the NSString property, the non-mutable
class promises the users of your API that it won’t mutate. You need a copy to
prevent changes behind your back. The performance hit is the price you pay to
prevent a bug.
copy is not a performance issue for NSString. It doesn’t copy anything, it just
increments the retain count and returns the same pointer. (Static/global
NSStrings don’t even bother to deallocate themselves.) Copying a mutable string
does allocate and initialize a new object; either way, the attribute does the
Right Thing.
— F
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