![NSNumber Literals
• NSNumber *anInt = [NSNumber numberWithInt: 10];
• NSNumber *aBool =[NSNumber numberWithBool: YES];
• NSNumber *aChar = *NSNumber numberWithChar: ‘z’+;
• Too much typing
• We have all used NSString literals such as @”this”
• NSNumber *aNum = @10;
• NSNumber *aBool = @YES;
• NSNumber *aChar = @’z’;](https://image.slidesharecdn.com/ios-whats-new-130506125230-phpapp02/85/iOS-Development-What-s-New-4-320.jpg)
![Arrays and Dictionaries
• To create a NSArray or NSDictionary, we need to use factory
methods such as:
• [NSArray arrayWithObjects: obj1, @"abc", obj3, nil];
• [NSDictionary dictionaryWithObjectsAndKeys: obj1, obj2, key1,
key2, nil];
• To access an object:
• [array objectAtIndex: 1];
• *dictionary objectForKey: @”key”+;
• To modify/update/change an object:
• [array replaceObjectAtIndex: 1 withObject: @"new object"];
• [dictionary setObject: @"new Object" forKey: @"key3"];](https://image.slidesharecdn.com/ios-whats-new-130506125230-phpapp02/85/iOS-Development-What-s-New-6-320.jpg)
iOS Development: What's New
- 1. iOS Development: What’s New April 24, 2013
- 2. Topics for Today • New Objective-C language features • Storyboard • UI Customization with UIAppearance • Some useful stuff I learned this term
- 3. Objective-C: New Features • NSNumber literals • Boxed expressions • NSArray & NSDictionary literals
- 4. NSNumber Literals • NSNumber *anInt = [NSNumber numberWithInt: 10]; • NSNumber *aBool =[NSNumber numberWithBool: YES]; • NSNumber *aChar = *NSNumber numberWithChar: ‘z’+; • Too much typing • We have all used NSString literals such as @”this” • NSNumber *aNum = @10; • NSNumber *aBool = @YES; • NSNumber *aChar = @’z’;
- 5. Boxed Expressions • @( <an expression> ) • Eg. NSNumber *aDouble = @(2 * pi * r); • Also works with cstrings, enums
- 6. Arrays and Dictionaries • To create a NSArray or NSDictionary, we need to use factory methods such as: • [NSArray arrayWithObjects: obj1, @"abc", obj3, nil]; • [NSDictionary dictionaryWithObjectsAndKeys: obj1, obj2, key1, key2, nil]; • To access an object: • [array objectAtIndex: 1]; • *dictionary objectForKey: @”key”+; • To modify/update/change an object: • [array replaceObjectAtIndex: 1 withObject: @"new object"]; • [dictionary setObject: @"new Object" forKey: @"key3"];
- 7. Container Literals • NSArray • @*@”one”, @”two”, @”three”+; • NSDictionary • Just like JSON • @, @”key1” : @”value1”, @”key2” : @”value2”- • No more confusing factory methods
- 8. Demo
- 9. Storyboard
- 11. What’s Storyboard? • A .storyboard is basically A huge XML file which contains XCode Interface Builder information • Comprised of individual “scenes” (Views + Controllers) • Transitions/Relationships between scenes are defined by “segues”
- 12. Advantages of Using Storyboards • Clearly defined flow • Less nib file cluttering • Reduce cluttering even more when you are making an universal app • Using segues saves you from writing millions of IBActions with repetitive push and pop view controller codes. • Too easy to use • Build a working UI prototype extremely fast with almost zero coding • Storyboard knows about view-controllers, so you can create more powerful views (eg. Static table view cells, prototype cells)
- 13. Disadvantages of Using Storyboards • Impossible to merge storyboard changes • Solution 1: Don’t work on it at the same time • Solution 2: Based on program flow, use multiple storyboards • Not backwards compatible with iOS 4- (also iOS 5 if you are using features such as embedded segue for container view)
- 14. How to Integrate Storyboard in Your App • Each project can have a main storyboard set in project settings • View controllers can also be loaded from storyboard files programmatically: • In this way, we can use multiple storyboards with NIBs.
- 15. Segues • A segue defines a visual transition OR relationship between two view controllers • Examples of transition segues: • Push segue (push view controller onto a navigation controller) • Modal segue (presenting a view controller modally) • Popover segue (Presenting a UIPopoverController, iPad only) • Custom segue (subclass UIStoryboardSegue and override the -perform method to do whatever you want. Can be reused in Storyboard) • Examples of relationship segues: • A empty navigation controller has a relationship segue to its root view controller • A container view has a embed segue to its child view controller
- 16. Performing Segue • Define a segue by ctrl-drag from a control (such as UIButton) to another view controller • Will be triggered when the specified action is performed on that control • Define a segue by ctrl-drag from a view controller to another view controller • Segue needs to be triggered manually by calling –performSegueWithIdentifier:sender:
- 18. Pass Data Between Controllers • Implement prepareForSegue:(UIStoryboardSegue *)sender:(id) in the view controller that will initiate the segue • This method is called before a segue is about to be performed • The UIStoryboardSegue parameter contains the following properties: identifier, sourceViewController, and destinationViewController • Now you can set properties and send messages to these controllers!
- 19. Unwind Segues • Unwind segue is a segue that jump back to previous scenes • To unwind from controller B back to controller A: 1. In controller A, create a method that takes a UIStoryboardSegue as parameter with return type IBAction 2. In storyboard, select controller B, ctrl-drag from a control to the “Exit” icon at the bottom of the controller 3. Select the method that you defined in B. The unwind segue has been created. 4. On the left panel of the interface builder, select the unwind segue and give it an identifier. 5. prepareForSegue:sender: will be called in B, and then the IBAction method in A will be called
- 20. Storyboard: Conclusion • You can avoid using delegation pattern in some cases if you use segues • With iOS 7 introduction due in June, we should start building new apps with storyboards (and autolayout)
- 21. UI Customization with UIAppearance Protocol • Customize UIKit objects (eg. UIView, UIButton,…) globally • Customize specific elements depending on view hierarchy
- 22. Demo
- 23. Useful iOS Stuff
- 24. Singleton Best Practices • Restricting instantiation of a class to one object only • Example: ServiceManager • One object is then shared by many • Issue: Instantiation in a multi-threaded environment
- 25. Basic Singleton • Not thread-safe
- 26. Mutex Lock • Takes lock every time when you only needs to lock it once. Expansive.
- 27. -Initialize • If you send any message to the class, singleton object will be created.
- 28. Double-checked Locking • Check if singleton is instantiated before and after taking lock • Memory barriers ensures all load and store CPU operations completes before proceeding • Doesn’t take lock every time, but still have to pay for OSMemoryBerrier()
- 29. Grand Central Dispatch • As fast as non-thread safe version • Similar to double checked locking, but avoid OSMemoryBarrier() penalty • Guaranteed run only once
- 30. Custom Container View Controllers • Embed multiple view controllers in one view controller • Adding, removing, and transition between child view controllers • Its like implementing your own UINavigationController or UITabBarController
- 31. Adding / Removing Child View Controllers
- 32. Transition Between Child View Controllers
- 33. Grand Central Dispatch is really good, but I don’t have time to finish the slide! • Efficient, fast C API • dispatch_sync, dispatch_async, dispatch_after to queue operations • dispatch_semaphore, dispatch_group, dispatch_barrier for synchronization • You can create your own serial OR concurrent queues with dispatch_queue_create • dispatch_apply for concurrent enumeration on an array • Create “dispatch sources” such as dispatch timers that attach to a queue and fire periodic events • Use dispatch_io to do sync/async operations on file descriptors
- 34. Thank you! • Any questions?