1. CONFIDENTIAL2013 GlobalLogic Inc. Interesting talks from NSConference 6 by Yuriy Berdnikov

2. 2013 GlobalLogic Inc. CONFIDENTIAL

3. CONFIDENTIAL Key Value Observing (KVO) Core Data Sync with Ensembles Dont reinvent the wheel. Why ?

4. CONFIDENTIAL Yearly event since 2009 More then 300 people attended this year Speakers - lead developers, book writers, etc. Some of them was performed on Apple WWDC. Balance between technical and UX material NSConference

5. CONFIDENTIAL Key Value Observing

6. CONFIDENTIAL What is KVO ? It provides a way for objects to get notified when the properties of other objects are changed. One object observes a key of another object. When the observed object changes the value of that key, the observer gets notified.

7. CONFIDENTIAL Subscribing

8. CONFIDENTIAL Responding

9. CONFIDENTIAL So how does that work, not needing any code in the observed object?

10. CONFIDENTIAL isa-swizzling It creates a brand new class at runtime that subclasses your class It overrides the set methods for any observed keys It switches out the isa pointer of your object

11. CONFIDENTIAL Sample

12. CONFIDENTIAL @interface TestClass : NSObject { int x; int y; int z; } @property int x; @property int y; @property int z; @end

13. CONFIDENTIAL static NSArray *ClassMethodNames(Class c) { NSMutableArray *array = [NSMutableArray array]; unsigned int methodCount = 0; Method *methodList = class_copyMethodList(c, &methodCount); for (unsigned int i = 0; i < methodCount; i++) [array addObject: NSStringFromSelector(method_getName(methodList[i]))]; free(methodList); return array; }

14. CONFIDENTIAL static void PrintDescription(NSString *name, id obj) { NSString *str = [NSString stringWithFormat: @"%@: %@nt NSObject class %snt libobjc class %snt implements methods ", name, obj, class_getName([obj class]), class_getName(obj->isa), [ClassMethodNames(obj->isa) componentsJoinedByString:@", ]]; printf("%sn", [str UTF8String]); }

15. CONFIDENTIAL int main(int argc, char **argv) { [NSAutoreleasePool new]; TestClass *x = [[TestClass alloc] init]; TestClass *y = [[TestClass alloc] init]; TestClass *xy = [[TestClass alloc] init]; TestClass *control = [[TestClass alloc] init]; [x addObserver:x forKeyPath:@"x" options:0 context:NULL]; [xy addObserver:xy forKeyPath:@"x" options:0 context:NULL]; [y addObserver:y forKeyPath:@"y" options:0 context:NULL]; [xy addObserver:xy forKeyPath:@"y" options:0 context:NULL]; PrintDescription(@"control", control); PrintDescription(@"x", x); PrintDescription(@"y", y); PrintDescription(@"xy", xy); return 0; }

16. CONFIDENTIAL Running the Code control: NSObject class TestClass libobjc class TestClass implements methods x: NSObject class TestClass libobjc class NSKVONotifying_TestClass implements methods y: NSObject class TestClass libobjc class NSKVONotifying_TestClass implements methods xy: NSObject class TestClass libobjc class NSKVONotifying_TestClass implements methods

17. CONFIDENTIAL Core Data Sync with Ensembles

18. CONFIDENTIAL Elements of Sync Identifying corresponding objects across stores Determining what has changed since the last sync Resolving conflicts due to concurrent changes

19. CONFIDENTIAL Ensembles Requires minimal changes to existing code Backend agnostic Eventual consistency of data across client devices Conflict resolution

20. CONFIDENTIAL github.com/drewmccormack/ensembles ensembles.io

21. CONFIDENTIAL Dont reinvent the wheel

22. CONFIDENTIAL Why ? Old code sucks 1000 solutions for 1000 problems, but you only need 1 Maintenance

23. CONFIDENTIAL

24. CONFIDENTIAL There is a good code! Manage risks Learn technologies that 3rd party code uses Write own frameworks

25. CONFIDENTIAL2013 GlobalLogic Inc. Q&A

26. CONFIDENTIAL2013 GlobalLogic Inc. Thank you