Apple code example, why are they accessing ivars directly here?

Question

Looking at the Apple example application for MultipeerGroupChat (specifically MainViewController.m):

https://developer.apple.com/library/ios/samplecode/MultipeerGroupChat/Listings/AdhocGroupChat_MainViewController_m.html#//apple_ref/doc/uid/DTS40013691-AdhocGroupChat_MainViewController_m-DontLinkElementID_8

The example contains the below code assigning properties:

@property (retain, nonatomic) NSMutableArray *transcripts;
@property (retain, nonatomic) NSMutableDictionary *imageNameIndex;

and then initializing them in viewDidLoad:

- (void)viewDidLoad
{
    [super viewDidLoad];

    // Init transcripts array to use as table view data source
    _transcripts = [NSMutableArray new];
    _imageNameIndex = [NSMutableDictionary new];

    ---SNIP---

Is there a reason they are assigning directly to the ivars _transcripts and _imageNameIndex? I thought proper convention dictates that you always use the properties to access the variables unless you are in an init method...indeed, a little further in the viewDidLoad method the author does use properties to assign other variables:

self.displayName = [defaults objectForKey:kNSDefaultDisplayName];

self.serviceType = [defaults objectForKey:kNSDefaultServiceType];

I know Apple example code has, in the past, sometimes strayed from good coding practices, so I'm wondering if this is just sloppy coding or if there is a valid reason to access those two ivars directly in a non-initialization method.

Answer 1

There is no definitive way for how properties have to be accessed. Seeing as this is just a demo project, the engineer who wrote this probably knew the scope of the project allowed for some shortcuts.

What's been done here isn't wrong, it just isn't recommended.