Question

In my AppDelegate, I download some data from the internet and store it into an array. I want one of my ViewControllers to access that array. How would I go about in doing so? Is this a good situation to implement a delegate or a protocol? If so, can someone recommend a good tutorial for that?

Thank you

EDIT:

Please note that the data refreshes upon each launch so there is no need for Core Data or plists. Furthermore, the data are custom objects which I created so they can’t be stored in a plist for example.

Answer 1

You have 2 options:

1. Implement a delegate protocol
2. Use NSNotifications

The advantages/disadvantages of each is set out well in this question and answer:
Delegates v Notifications

As notifications are easier to implement and may well be sufficient for your needs, you can implement it with the following steps:

1. In the class where you download the data:
   When the data has been downloaded and the array populated, include the following lines:

NSDictionary *dict = [NSDictionary dictionaryWithObject:array forKey:@"Data"];
[[NSNotificationCenter defaultCenter] postNotificationName:@"DataDownloaded" object:self userInfo:dict];

2. In the class where you want to receive the data:

2.1 Add the following line to your viewDidLoad method:

`[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(dataDownloaded:) name:@"DataDownloaded" object:nil];

2.2 Create the dataDownloaded selector:

• (void)dataDownloaded:(NSNotification *)note {

  NSDictionary *dict = note.userInfo;
NSArray *dataArray = [note.userInfo objectForKey:@"DataDownloaded"];

2.3 Add the following line to dealloc and viewDidUnload:

[[[NSNotificationCenter defaultCenter] removeObserver:self];