Question About Retain Counts & initializing member variables

Question

Imagine I have a member variable

@property(nonatomic,retain)NSArray *array;

Now in my viewDidLoad I set up a simple array

array = [[NSArray alloc]initWithObjects:@"A",@"B","C",nil];

My retain count for array is going to be 1 right?

Now if I were to set up the array using the accessor method

self.array = [[NSArray alloc]initWithObjects:@"A",@"B","C",nil];

Is my retain count 2 because my accessor method bumps the retain count up by 1?

What's the convention for initializing member variables?

That's a property, not a member variable. They're two very different things. — BoltClock, Feb 11 '11 at 18:02
Note also that Objective-C does not have member variables. It has instance variables instead. (More or less the same, but using the right terminology is helpful.) — bbum, Feb 11 '11 at 22:30

BoltClock · Accepted Answer · 2011-02-11T18:14:53.523

That is correct, the retain count for self.array = ends up as 2.

First, you alloc init a new NSArray object. That's a retain count of 1. Second, your setter sends the object a retain message when assigning it to your instance var. That bumps the retain count up to 2.

What's the convention for initializing member variables?

Besides directly setting the ivar array = as in your question, here are some ways to do this with your self.array property without leaking:

Autorelease:

self.array = [[[NSArray alloc] initWithObjects:@"A", @"B", @"C", nil] autorelease];

Use the arrayWithObjects: class method. Simpler, and also produces an autoreleased object:
```
self.array = [NSArray arrayWithObjects:@"A", @"B", @"C", nil];
```
Make a temporary variable to hold the new pointer, then release it after setting the property (which will have had it retained by then):
```
NSArray *tmpArray = [[NSArray alloc] initWithObjects:@"A", @"B", @"C", nil];
self.array = tmpArray;
[tmpArray release];
```

What about using the first option array = [[NSArray alloc]initWithObjects:....]; It seems the simplest why don't you suggest that one? — aaronium112, Feb 13 '11 at 16:12

Question About Retain Counts & initializing member variables

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