CODEWITHSUNDEEP
objective-cios
patrick
patrick

Reputation: 9722

what does "property with 'weak' attribute must be of object type" really mean?

I have this in my interface:

@property (nonatomic, weak) NSTimeInterval *timeStamp;

Which my logic told me, I need a time stamp object, that only is going to be used by this class within the context of its instantiation, so "weak" seemed to be logical to me-- but XCode tells me "property with 'weak' attribute must be of object type"... If I just do:

@property (nonatomic) NSTimeInterval *timeStamp;

Then the error goes away, but I am not sure I understand why...

Upvotes: 8

Views: 10286

Answers (1)

user457812
user457812

Reputation:

The problem is that NSTimeInterval is a value type -- it's an alias for double, essentially (check NSDate.h for the typedef). The weak attribute only applies to objects that have a retain count (that is, anything that descends from NSObject or NSProxy).

As such, storing a pointer to NSTimeInterval is probably a mistake on your part. You will most likely never receive a pointer to an NSTimeInterval unless you're expected to write to a given address as an output to a function (probably a callback in such a case). That said, I'm not aware of any functions with NSTimeInterval * as a return type nor any that pass the same to a callback.

Upvotes: 14

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