IOS app breakpoints at startup

I am an experienced developer but new to iOS / Objective C.

The application below builds OK (mod any typo / cut'n'paste errors). When I run it, it breaks in the print method, which makes it look like some kind of bug. I don't see what and where is the error. Probably a real new bug though!

Can anyone help me explain what I am doing wrong and how to fix it?

This is a command line macOS application with Foundation that is built and run in Xcode.

@interface DayOfYear : NSObject
- (void) print;
- (id) init : (int) day;
@end // DayOfYear

@implementation DayOfYear

int dayInYr =0;

- (id) init : (int) day {
    self = [super init];
    dayInYr = day;
    return self;
}

- (void) print {
     // NSLog(@"In print with %d", dayInYr);

}    // WHEN RUN THIS IS WHERE IT BREAKPOINTS SAYING "Thread 1, breakpoint 1.1, 2.1


@end

int main(int argc, const char * argv[])
{

    @autoreleasepool {

        // insert code here...
        NSLog(@"Hello, World!");

        DayOfYear *d =[[DayOfYear alloc] init : 2 ];
        [d print];


        NSLog(@"Finished!");

    }
    return 0;
}