Question

OK, this must have been asked before but I looked like mad and found nothing:

I have a simple array in my iphone app which I define like so:

@property (nonatomic, strong) NSArray *pages;
@synthesize pages = _pages;

I’ve seen this in Apples sample code and thought this is a nice short-cut for writing self.pages (i.e. _pages replaces self.pages) like so:

_pages = [[NSArray alloc] init];

but then Apple has this again (not exactly like this, but it appears as if they keep swapping randomly):

self.pages = [NSKeyedUnarchiver unarchiveObjectWithData:contents];

And finally:

[_pages release];

Which totally confuses me. What would be the difference between _pages and self.pages?

Thanks for your help.

Answer 1

_pages is the name of the object’s ivar. pages is the property name which is different.
So, @synthesize pages = _pages; finally tells that pages is the property for the ivar _pages.

You will encouter the ivar direct access via _pages in initializers and dealloc methods. Every where else, the property name is used to get/set its value.