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Numbers and mutable sets and retain counts, oh my!
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Numbers and mutable sets and retain counts, oh my!


  • Subject: Numbers and mutable sets and retain counts, oh my!
  • From: William Squires <email@hidden>
  • Date: Sat, 13 Nov 2010 08:57:40 -0600

Okay, so I'm getting a bit melodramatic...

Let's say I have some sample code that looks like:

-(NSMutableSet *)allOddNumbersExcept5Set
{
NSMutableSet *results = [[NSMutableSet alloc] initWithCapacity:1];

for (int i=1; i<=10; i+=2)
  {
  if (i != 5)
    {
    NSString *testNumber = [NSString stringWithFormat:"%d", i];
    // testNumber should now be an autoreleased NSString
    [results addObject:testNumber];
    }
  }
return results;
}

Questions:
1) Do mutable containers (NSMutableArray, NSMutableDictionary, NSMutableSet) always send the 'retain' message to objects added with the 'addObject:' message?
2) When you retrieve the results from the collection, does the object reference you get back have the same retain count as the one in the container? (i.e. if I add an object to an NSMutableArray (held in an @property) in one method, and retrieve it in another, will I get a retain count of 1 or 2?)
3) Will the above code autorelease the 'testNumber' the second (and third, and fourth...) times through the loop when it gets another autoreleased NSString, or will it just re-use the existing one?
4) Would I be better off with:


-(NSMutableSet *)allOddNumbersExcept5Set
{
NSMutableSet *results = [[NSMutableSet alloc] initWithCapacity:1];

for (int i=1; i<=10; i+=2)
  {
  if (i != 5)
    {
    NSString *testNumber = [[NSString alloc] initWithFormat:@"%d", i];
    [results addObject:testNumber];
    [testNumber release];
    }
  }
return results;
}

instead?

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