Learning iOS: Part 1

This deck focuses on understanding some of the basics of Objective-C and how it is compiled for iOS.

Transcript

1. learning iOS @nystrorm github.com/rnystrom
2. requirements
3. osx 10.8
4. xcode 4.5
5. objective C
6. objective c is a better C
7. objective c is a better C p (quite)
8. pointers
9. NSString *a = @”Hello World!”; NSString *b = a; a = @”New world”; NSLog(@”%@”,b); // New world
10. structs
11. struct CGSize { CGFloat width; CGFloat height; }; CGSize size = { 100.f, 200.f }; size.width = 150.f;
12. primitives
13. // avoid int i = 3; float f = 3.14f; // architecture safe NSInteger i = 3; CGFloat f = 3.14f; // legal i = f;
14. #if __LP64__ typedef long NSInteger; #else typedef int NSInteger; #endif
15. messages (aka functions)
16. - (NSInteger) indexForCell:(UITableViewCell*)cell; return type name param type param var
17. - (NSInteger) doSomethingWithText:(NSString*)text width:(CGFloat)width wordCount:(NSInteger)count { // whitespace doesn’t matter return [text length] * count + width; }
18. - (void) instanceMethod; + (void) classMethod;
19. verbose is ok be consistent and follow conventions
20. @class BabyBack; - (void)iWantMyBabyBack:(BabyBack*)babyBack;
21. objects
22. // declare the class and superclass @interface MyObject : NSObject // public properties @property (strong, nonatomic) NSString *title; // method signatures - (void)doSomethingWithText:(NSString*)text; @end
23. #import "MyObject.h" @implementation MyObject - (void)doSomethingWithText:(NSString *)text { self.title = text; // do something cool } @end
24. // create an object stored in memory MyObject *object = [[MyObject alloc] init]; // using an object’s property object.title = @"Hello World!"; // using an object’s methods [object doSomethingWithText:@”Change me”];
25. properties
26. one @property declaration sets up
27. one @property declaration sets up instance variable
28. one @property declaration sets up instance variable getter / setter
29. one @property declaration sets up instance variable getter / setter thread safety
30. one @property declaration sets up instance variable getter / setter thread safety retention / ownership
31. one @property declaration sets up instance variable getter / setter thread safety retention / ownership (what)
32. references
33. every time an object NSObject *object = [[NSObject alloc] init]; // ref = 1
34. every time an object NSObject *object = [[NSObject alloc] init]; // ref = 1 gets referenced anotherObject.property = object; // ref = 2
35. every time an object NSObject *object = [[NSObject alloc] init]; // ref = 1 gets referenced anotherObject.property = object; // ref = 2 that object’s reference count is increased
36. object memory is never deallocated unless the reference count is zero (almost)
37. automatic
38. automatic reference
39. automatic reference counting
40. garbage collector?
41. NO
42. ARC automatically counts an object’s references and deallocates them when reaching zero
43. ARC automatically counts an object’s references and deallocates them when reaching zero
44. ARC automatically counts an object’s references and deallocates them when reaching zero
45. ARC manages memory just be be mindful of memory usage (appease the binary gods)
46. nibs live demo
47. more info apple docs raywenderlich.com ask me!