Objective-C Sins - Speaker Deck

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Objective-C Sins

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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.

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@mb

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matthew bischoff

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matt

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Velocity Quotebook

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Sins

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[object retainCount];

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Why not?

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Object retainCount? Actual retainCount [NSNumber numberWithInt:1] 1 2 @"Matt" 1 1152921504606846975 [NSString stringWithString:@"Matt"] 1 1152921504606846975

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Key-Value Observing

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Key-Value Observing has the worst API in all of Cocoa. It’s awkward, verbose, and confusing. Mattt Thompson

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“Stringly Typed”

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Refactoring is scary.

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Throws Exceptions

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ARC == garbage collection

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You still have to pay attention.

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. Syntax [ ] Syntax

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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

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Dot syntax is for properties.

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Bracket syntax is for methods.

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UIColor.clearColor; array.count; object.hash;

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More than 1 Class per file

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performSelector: afterDelay:

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It’s a crash waiting to happen.

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Missing or improper reuse

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Always reuse cells.

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Don’t keep track of cells.

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Architecture-dependent primitive types

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int float double

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NSInteger / NSUInteger CGFloat NSTimeInterval

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Violating MVC

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Models that do networking

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Views that know about models

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Controllers that do layout

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NSDictionary

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Not a replacement for a model

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✨"

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Magic numbers

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Repeating yourself Repeating yourself Repeating yourself Repeating yourself Repeating yourself Repeating yourself

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Every piece of knowledge must have a single, unambiguous, authoritative representation within a system. Andy Hunt and Dave Thomas

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if (taylorSwift) { taylorSwift.age = 22; }

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Singletons

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Blocking the main queue

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Low level APIs

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CoreFoundation CoreText CoreGraphics CoreAnimation

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Foundation TextKit UIKit UIView Animations

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@property (nonatomic, strong, readwrite) NSString *title;

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@property (nonatomic) NSString *title;

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@property NSString *title;

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Warnings

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Unused Variable ‘sin’ !

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Unused Variable ‘sin’ !

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Public and readwrite

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Missing #pragma marks

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#pragma mark - NSObject ! - (void)dealloc {} ! #pragma mark - UIViewController ! - (void)viewDidLoad {} ! #pragma mark - LCKDocumentsTableViewController ! - (void)setupRefreshControl {}

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Bad names

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UIImage *img; UIButton *btn; NSString *str; NSArray *arr; NSDictionary *dict; NSInteger i;

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UIImage *avatar; UIButton *signupButton; NSString *name; NSArray *people; NSDictionary *userInfo; NSInteger count;

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Two-letter prefixes

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NS UI CG CA AC ST XC SK MF AD

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Two-letter preﬁxes…are reserved by Apple for use in framework classes. ! Your own classes should use three letter preﬁxes.

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Inconsistent style

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Not overriding the designated initializer

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- (instancetype)initWithPerson:(LCKPerson *)person { self = [super initWithStyle:UITableViewStylePlain]; if (self) { _person = person; _dataStore = [NSMutableDictionary dictionary]; } return self; }

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- (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; }

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UITapGestureRecognizer

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Just use a UIButton.

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UISwipeGestureRecognizer

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Just use a UIPanGestureRecognizer.

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Inaccessibility

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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”

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Missing Localization

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// Unnecessary comments

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Comments explain why. Not what or how.

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true && false

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YES and and NO

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Profiling at the end

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[[[[[too much] code] on] one] line]

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#import

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#define

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retain cycles

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Object Object strong

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[self.queue addOperationWithBlock:^{ [self download]; }];

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__weak typeof(self) weakSelf = self; [self.queue addOperationWithBlock:^{ [weakSelf download]; }];

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(assign) delegates

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self.webView.delegate = nil;

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Blended layers

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Mixing up nothing

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nil, Nil, NULL, NSNull

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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