Understanding "release"

[thomashw]

I've bolded the part of the code I don't fully understand.

 

• Won't sum = sum2 just overwrite the old sum? So why do you need to release it beforehand?
  
• Why isn't sum2 released at the end of the program? Should it be?
  

 

#import “Fraction.h”

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

NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
Fraction *aFraction = [[Fraction alloc] init]; Fraction *sum = [[Fraction alloc] init], *sum2; int i, n, pow2;

[sum setTo: 0 over: 1]; // set 1st fraction to 0

NSLog (@”Enter your value for n:”);
scanf (“%i”, &n);
pow2 = 2;

for (i = 1; i <= n; ++i) {
     [aFraction setTo: 1 over: pow2];
     sum2 = [sum add: aFraction];
[b]    [sum release]; // release previous sum
     sum = sum2;[/b]
     pow2 *= 2;
}

NSLog (@”After %i iterations, the sum is %g”, n, [sum convertToNum]); [aFraction release];
[sum release];
[pool drain];

return 0;
}

 

Thank you!!

[thomashw]

Bump.