exercise 17-2

[mdziedzic]

Code: (Objective-C)

#import <Foundation/Foundation.h>

int main (int argc, const char * argv[]) {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

	NSMutableArray *treats = [NSMutableArray arrayWithCapacity: 3];
	NSMutableString *str1 = [NSMutableString stringWithString: @"lemon curd tart"];
	NSMutableString *str2 = [NSMutableString stringWithString: @"dark chocolate"];
	NSMutableString *str3 = [NSMutableString stringWithString: @"peppermint ice cream"];
	NSMutableString *str4 = [NSMutableString stringWithString: @"rhubarb pie"];
	
	NSLog(@"str1 retain count = %x", [str1 retainCount]);
	NSLog(@"str2 retain count = %x", [str2 retainCount]);
	NSLog(@"str3 retain count = %x", [str3 retainCount]);
	NSLog(@"str4 retain count = %x", [str4 retainCount]);
		
	[treats addObject: str1];
	[treats addObject: str2];
	[treats addObject: str3];
	
	NSLog(@"\n");
	NSLog(@"after adding str1, str2, str3 to array treats:");
	NSLog(@"str1 retain count = %x", [str1 retainCount]);
	NSLog(@"str2 retain count = %x", [str2 retainCount]);
	NSLog(@"str3 retain count = %x", [str3 retainCount]);
	NSLog(@"str4 retain count = %x", [str4 retainCount]);
	
	[treats replaceObjectAtIndex: 1 withObject: str4];
	
	NSLog(@"\n");
	NSLog(@"after replacing str2 with str4 in array treats:");
	NSLog(@"str1 retain count = %x", [str1 retainCount]);
	NSLog(@"str2 retain count = %x", [str2 retainCount]);
	NSLog(@"str3 retain count = %x", [str3 retainCount]);
	NSLog(@"str4 retain count = %x", [str4 retainCount]);
	
	[pool drain];
    return 0;
}

str1 retain count = 1
str2 retain count = 1
str3 retain count = 1
str4 retain count = 1

after adding str1, str2, str3 to array treats:
str1 retain count = 2
str2 retain count = 2
str3 retain count = 2
str4 retain count = 1

after replacing str2 with str4 in array treats:
str1 retain count = 2
str2 retain count = 1
str3 retain count = 2
str4 retain count = 2

[john67]

Just want to point out to anyone copying this - there is a small error (which you most likely pick up by now if you've got this far in the book!!), doesn't stop the program from running but is the format specifier: %x should be %lx