Programming in Objective-C, Fifth Edition

Classes Owning Their Objects

Can you explain the output from Program 8.5?

Program 8.5.

#import "Rectangle.h"#import "XYPoint.h"int main (int argc, char * argv[]){   @autoreleasepool {      Rectangle *myRect = [[Rectangle alloc] init];      XYPoint   *myPoint = [[XYPoint alloc] init];      [myPoint setX: 100 andY: 200];      [myRect setWidth: 5 andHeight: 8];      myRect.origin = myPoint;      NSLog (@"Origin at (%i, %i)", myRect.origin.x, myRect.origin.y);      [myPoint setX: 50 andY: 50];      NSLog (@"Origin at (%i, %i)", myRect.origin.x, myRect.origin.y);   }   return 0;}

Program 8.5. Output

Origin at (100, 200)Origin at (50, 50)

You changed myPoint from (100, 200) in the program to (50, 50), and apparently it also changed the rectangle’s ...