Programming in Objective-C, Sixth Edition

Shallow Versus Deep Copying

Program 18.1 fills the elements of dataArray with immutable strings. (Recall that constant string objects are immutable.) In Program 18.2, you fill it with mutable strings instead so that you can change one of the strings in the array. Take a look at Program 18.2 and see whether you understand its output.

Program 18.2

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#import <Foundation/Foundation.h>int main (int argc, char * argv[]){   @autoreleasepool {      NSMutableArray    *dataArray = [NSMutableArray arrayWithObjects:         [NSMutableString stringWithString: @"one"],         [NSMutableString stringWithString: @"two"],         [NSMutableString stringWithString: @"three"],         nil      ];      NSMutableArray    *dataArray2; ...