Question

Let’s say we have a class with an NSTimeInterval property:

@interface MyClass : NSObject {
    NSTimeInterval timeSpent;
}
@property (assign) NSTimeInterval timeSpent;

I can then get the type of the property like so:

const char * type = property_getAttributes(class_getProperty([MyClass class], "timeSpent"));

…where type would be something like: Td, VtimeSpan with “d” indicating that it’s a double (which is normal since docs says typedef double NSTimeInterval)

Is there anything I can do in order to find out that the timeSpent property was initially declared as a NSTimeInterval?

Thanks !

Answer 1

You can’t. NSTimeInterval is a typedef of double, which means that it is exactly the same type with a new name. This is convenient for writing self-documenting code, but it doesn’t change anything about the type. (It also allows the underlying type to be changed while remaining source-compatible; they could change NSTimeInterval to be an alias of float or _Complex double or something else entirely, and your code wouldn’t need to care.)

Is there a reason you care? Are you trying to write some generic code that treats time intervals differently than regular numbers? What’s the end goal you have?