Objective-C Sins

I have a confession to make. I've written some terrible Objective-C code. I guess you can say I've sinned. In this talk, I discuss common anti-patterns and how to avoid them.

This talk was originally presented to students of the iOS class at The Flatiron School. Without the actual talking to go with it, these slides are probably missing a lot of context. If you're confused about something, send me a message on twitter (@mb).

Transcript

2. Objective-C Sins
3. sin 1 |sin| noun an immoral act considered to be a transgression against divine law: a sin in the eyes of God | the human capacity for sin. ! • an act regarded as a serious or regrettable fault, offense, or omission: he committed the unforgivable sin of refusing to give interviews | humorous : with air like this, it's a sin not to go out.
4. sin 1 |sin| noun an immoral act considered to be a transgression against divine law: a sin in the eyes of God | the human capacity for sin. ! • an act regarded as a serious or regrettable fault, offense, or omission: he committed the unforgivable sin of refusing to give interviews | humorous : with air like this, it's a sin not to go out.
5. @mb
6. matthew bischoff
7. matt
9. Velocity Quotebook
12. Sins
13. [object retainCount];
15. Why not?
16. Object retainCount? Actual retainCount [NSNumber numberWithInt:1] 1 2 @"Matt" 1 1152921504606846975 [NSString stringWithString:@"Matt"] 1 1152921504606846975
17. Key-Value Observing
18. Key-Value Observing has the worst API in all of Cocoa. It’s awkward, verbose, and confusing. Mattt Thompson
19. “Stringly Typed”
20. Refactoring is scary.
21. Throws Exceptions
22. ARC == garbage collection
23. You still have to pay attention.
24. . Syntax [ ] Syntax
25. What’s the obvious thing to do, the easiest way to agree? Just do what the headers say. If it’s a property, treat it as such. If it’s not, don’t. ! And when in doubt, look it up. Brent Simmons
26. Dot syntax is for properties.
27. Bracket syntax is for methods.
28. UIColor.clearColor; array.count; object.hash;
29. More than 1 Class per file
31. performSelector: afterDelay:
32. It’s a crash waiting to happen.
33. Missing or improper reuse
34. Always reuse cells.
35. Don’t keep track of cells.
36. Architecture-dependent primitive types
37. int float double
38. NSInteger / NSUInteger CGFloat NSTimeInterval
39. Violating MVC
40. Models that do networking
41. Views that know about models
42. Controllers that do layout
43. NSDictionary
44. Not a replacement for a model
45. ✨"
46. Magic numbers
47. Repeating yourself Repeating yourself Repeating yourself Repeating yourself Repeating yourself Repeating yourself
48. Every piece of knowledge must have a single, unambiguous, authoritative representation within a system. Andy Hunt and Dave Thomas
49. if (taylorSwift) { taylorSwift.age = 22; }
50. id
51. Singletons
52. Blocking the main queue
53. Low level APIs
54. CoreFoundation CoreText CoreGraphics CoreAnimation
55. Foundation TextKit UIKit UIView Animations
56. @property (nonatomic, strong, readwrite) NSString *title;
57. @property (nonatomic) NSString *title;
58. @property NSString *title;
59. Warnings
60. Unused Variable ‘sin’ !
61. Unused Variable ‘sin’ !
62. Public and readwrite
63. Missing #pragma marks
64. #pragma mark - NSObject ! - (void)dealloc {} ! #pragma mark - UIViewController ! - (void)viewDidLoad {} ! #pragma mark - LCKDocumentsTableViewController ! - (void)setupRefreshControl {}
65. Bad names
66. UIImage *img; UIButton *btn; NSString *str; NSArray *arr; NSDictionary *dict; NSInteger i;
67. UIImage *avatar; UIButton *signupButton; NSString *name; NSArray *people; NSDictionary *userInfo; NSInteger count;
68. Two-letter prefixes
69. NS UI CG CA AC ST XC SK MF AD
70. Two-letter prefixes…are reserved by Apple for use in framework classes. ! Your own classes should use three letter prefixes.
71. Inconsistent style
73. Not overriding the designated initializer
74. - (instancetype)initWithPerson:(LCKPerson *)person { self = [super initWithStyle:UITableViewStylePlain]; if (self) { _person = person; _dataStore = [NSMutableDictionary dictionary]; } return self; }
75. - (id)initWithStyle:(UITableViewStyle)style { return [self initWithPerson:nil]; } ! - (instancetype)initWithPerson:(LCKPerson *)person { self = [super initWithStyle:UITableViewStylePlain]; if (self) { _person = person; _dataStore = [NSMutableDictionary dictionary]; } return self; }
76. UITapGestureRecognizer
77. Just use a UIButton.
78. UISwipeGestureRecognizer
79. Just use a UIPanGestureRecognizer.
80. Inaccessibility
82. Property Description Example accessibilityLabel Identifies the accessibility element, but does not include the type of the control or view “Share” accessibilityValue The value is a localized string that contains the current value of an element “35 %” accessibilityHint Description of the result of performing an action on the element. “Selects the message”
83. Missing Localization
85. // Unnecessary comments
86. Comments explain why. Not what or how.
87. true && false
88. YES and and NO
89. Profiling at the end
91. [[[[[too much] code] on] one] line]
92. #import <objc/runtime.h>
93. #define
94. retain cycles
95. Object Object strong
96. [self.queue addOperationWithBlock:^{ [self download]; }];
97. __weak typeof(self) weakSelf = self; [self.queue addOperationWithBlock:^{ [weakSelf download]; }];
98. (assign) delegates
99. self.webView.delegate = nil;
100. Blended layers
103. Mixing up nothing
104. nil, Nil, NULL, NSNull
105. Symbol Value Meaning NULL (void *)0 literal null value for C pointers nil (id)0 literal null value for Objective-C objects Nil (Class)0 literal null value for Objective-C classes NSNull [NSNull null] singleton object used to represent null
106. Ignoring crash logs
108. Special Thanks •Ash Furrow •Brent Simmons •Mattt Thompson •Brian Capps
109. Thank you.
110. Questions?