Question

I just recently made the move to Objective-C. I am doing some exercises from Kochan’s Programming in Objective-C 2.0. On this particular exercise, I am asked to modify the print method with and optional argument:

-(void)print{
  NSLog(@" %i/%i ", numerator, denominator);
}

For this I simply created another print method that would take a BOOL argument and modified the existing print method as follows:

-(void)print{
  [self printReduced:FALSE];
}
-(void)printReduced:(BOOL)r{
  if(r){
    [self reduce];
  }
  NSLog(@" %i/%i ", numerator, denominator);
}

But for the last part of the exercise, I am supposed to use that BOOL to determine if the Fraction should be reduced or not (no problem testing the flag), but when reduced I am not supposed to modify the original object. For this I allocated a new Fraction object inside the printReduced method and released it before the end of the method too:

-(void)printReduced:(BOOL)r{
  Fraction *printingFraction = [[Fraction alloc] init];
  [printingFraction setTo:numerator over:denominator];
  if(r){
    [printingFraction reduce];
  }
  NSLog(@" %i/%i ",[printingFraction numerator], [printingFraction denominator]);
  [printingFraction release];
}

My question is: Is it right to create and release objects whithin a given method this way? This seems to do the work just fine without modifying the original Fraction, but is this the right approach?

Answer 1

This is correct. Whenever you ‘alloc’ an object, you own it. Before it goes out of scope (the end of the method in this case), you must relinquish ownership, a release in this case.