Dereferencing a pointer when using NSLog in Objective-C

Question

NSDate *now = [NSDate date];
NSLog(@"This NSDate object lives at %p", now);
NSLog(@"The date is %@", now);

Ok, from this code, I know that now is a pointer to an NSDate object, but on the code at line 3, how can you dereference a pointer without an asterisk? Why don't we do code like this on the 3rd line:

NSLog(@"The date is %@", *now);

Answer 1

%@ takes a pointer to an object and sends it the description message, which returns an NSString pointer. (You can override description in your classes to customize the string.)

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Added in response to comment:

In Objective-C, you to send messages to objects via a pointer using the [ objectPointer message ] syntax. So, using your NSDate example, you can do:

NSDate * now = [NSDate date];
NSString * dateDescription = [now description];    // Note that "now" points to an object and this line sends it the "description" message
NSLog(dateDescription);

Any instance of a class that inherits from NSObject can be sent the description message and thus a pointer to it can be passed to an %@ format parameter.

(Technical note: if the object supports the descriptionWithLocale: message, it will be sent that instead.)

Answer 2

The %@ format specifier takes a pointer to an object, so there's no need to dereference the pointer in the parameter list. In general, there's no need to dereference pointers to Objective C objects.