what does "property with 'weak' attribute must be of object type" really mean?
ios, objective-c
Solution
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.
Problem
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...