dot self notation in nsxmlparser - iphone

Question

I was just reading an answer to a different question on nsxmlparsing.. and in it the guy was saying you should use self. notation for better memory management... what dose this mean?
I have left this out of initializing my dictionary should I have it in? how dose it help or not help?
- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qualifiedName attributes:(NSDictionary *)attributeDict
{
if ([elementName isEqualToString:#"Row"])
{
ICRow = [[NSMutableDictionary alloc] initWithDictionary:attributeDict];
}
if ([elementName isEqualToString:#"Rows"]) {
self.ICRows = [NSMutableArray arrayWithCapacity:8];
}
}

Answer 1

bar = self.foo;
is just a shorthand notation for
bar = [self foo];
and
self.foo = bar;
is shorthand for
[self setFoo:bar];
In terms of memory management this just means that the specific setters and getters are invoked, whereas
foo = bar
would simply assign the value (i.e. mostly just copy the pointer).
Say you have a retained property
#property (nonatomic, retain) FooType *foo;
//...
#synthesize foo;
then the setter might look like
- (void) setFoo:(FooType*)x
{
[x retain];
[foo release];
foo = x;
}
Now if you do a
FooType *newFoo = [[FooType alloc] init];
[self setFoo:newFoo];
// or self.foo = newFoo
Everything would be allright, since your previously allocated object is released and the new object is retained properly. If you instead just did a
foo = newFoo;
without thinking about to release the old and retain the new object, you would be leaking memory or worse...