MapStack - lesson 6

Transcript

2. Favoriting a location In the detail view controller, we use NSUserDefaults to store a location id inside an array when the user taps the favorite button.
3. The cascading pattern NSUserDefaults gives us a quick-and-dirty way to store id’s, but how to inform our favorites view that a new location is favorited? The are several ways but we’ll use the cascading pattern which leverages the app delegate to propagate the change.
4. UINavigationController We’ve seen two of the big three ways to handle navigation in iOS: 1) UITabbarController which handles the overall structure of our app. 2) Modal presentation which handled the details of our locations UINavigationController is the third common way to handle navigation iOS.
5. UINavigationController For our favorites view, when a user taps a cell, the navigation controller will slide the detail view horizontally onto the UIWindow.
6. UINavigationController The diagram shows view controllers being pushed onto the stack
7. UINavigationController The fact that UINavigationController is a subclass of UIViewController but also has a UIViewController property shouldn’t scare you. This pattern is not uncommon in cocoa.
8. pushing controllers onto the navigation stack Here is a view controller being pushed onto the navigation stack. Compare this to lesson 4 when we presented view controller from the bottom as modals.
9. Subclassing UITableViewCell When the stock table view cell isn’t good enough. We need our cell to have 2 label objects, 2 button objects, and an image view object.
10. Subclassing UITableViewCell MSTableViewCell can show a location detail, delete itself and can layout views with more flexibility
11. Creating our own delegates and protocols For ‘delete’ and ‘details’ to work, we need to create our own delegate pattern. We could use cellForRowAtIndexPath like before for one button, but we would still need a delegate to handle the other button.
12. Why are protocols confusing? Because the delegate is the servant and the object that owns the delegate property is the boss BUT the servant is often a superview of the boss!
13. Why are protocols confusing?
14. Why is the delegate property declaration weak? Recall that if it were strong, it would increment delegate’s retain count by 1. Our instance of MSTableViewCell would own the delegate. But in our favorite’s view, we’re assigning self to the delegate.
15. Why is the delegate property declaration weak? But when we created the local variable ‘cell’, we’re creating a strong pointer to that cell. If the cell’s pointer to its delegate were strong, then assigning the view controller to the delegate would create a retain cycle
16. preventing retain cycles Retain cycle cause memory leaks because the retain count never reaches 0 and, therefore, the memory is never deallocated.
17. preventing retain cycles
18. Basic networking to get locations from a server We use 3 objects NSMutableURLRequest, NSURLSession, and NSURLSessionDataTask to get data from a server. Like other managers we’ve used, they’re just subclasses of NSObject but with extra properties and methods to facilitate interactive with a remote server.
19. NSMutableURLRequest, NSURLSession, and NSURLSessionDataTask Build the URL: Build the networking session: Execute the download:
20. NSMutableURLRequest, NSURLSession, and NSURLSessionDataTask MSMapViewController has more detailed comments along with control flow to help you understand
21. AFNetworking Using NSURL, NSMutableURLRequest, NSURLSession, and NSURLSessionDataTask by themselves, while powerful, are missing features that a full-fledged, network-based application may need. Many companies and indie developers use the AFNetworking 3rd-party library which uses these objects under the hood.