The Evolution of a Cocoa Programmer

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The evolution of a Cocoa Programmer Chris Eidhof Mobile Central Europe 2014

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Hashtags #mceconf #mce-evolution

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commit c416c1d259bddaa74833e6df5acd770f85622293 Author: Chris Eidhof Date: Wed Jan 7 11:54:34 2009 +0100 Empty project

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I thought I was a pretty good programmer

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I knew PHP, Ruby and Haskell

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How hard can it be?

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Example code @interface HiscoreTableViewCell : UITableViewCell { IBOutlet UIImageView *badge; IBOutlet UILabel *badgeTitle; IBOutlet UILabel *name1; IBOutlet UILabel *name2; IBOutlet UILabel *name3; IBOutlet UILabel *position1; IBOutlet UILabel *position2; IBOutlet UILabel *position3; IBOutlet UILabel *score1; IBOutlet UILabel *score2; IBOutlet UILabel *score3; }

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Example code (continued) @property (nonatomic,readonly) UIImageView* badge; @property (nonatomic,readonly) UILabel *badgeTitle; @property (nonatomic,readonly) UILabel *name1; @property (nonatomic,readonly) UILabel *name2; @property (nonatomic,readonly) UILabel *name3; @property (nonatomic,readonly) UILabel *position1; @property (nonatomic,readonly) UILabel *position2; @property (nonatomic,readonly) UILabel *position3; @property (nonatomic,readonly) UILabel *score1;

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Example code (continued) @synthesize badge; @synthesize badgeTitle; @synthesize name1; @synthesize name2; @synthesize name3; @synthesize position1; @synthesize position2; @synthesize position3; @synthesize score1; @synthesize score2; @synthesize score3;

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There's more

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//TODO: as of here, it is completely broken if ([gameView superview] != nil) { [[SoundBoard sharedSoundBoard] startMenuTune]; [menuViewController viewWillAppear:YES]; [gameViewController viewWillDisappear:YES]; [gameView removeFromSuperview]; [gameViewController viewDidDisappear:YES]; [menuViewController viewDidAppear:YES]; } else {

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NSURL *cgiUrl = [NSURL URLWithString:POST_SCORE_URL]; NSMutableURLRequest *p = [NSMutableURLRequest requestWithURL:cgiUrl]; [p setTimeoutInterval:4]; [p setHTTPMethod:@"POST"]; [p setHTTPBody:requestData]; NSURLResponse *response = nil; NSError *error = nil; NSData *responseData = [NSURLConnection sendSynchronousRequest:p returningResponse:&response error:&error];

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How did I get better?

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If there's only one thing you'll remember Write code for the person after you

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EDD Embarassment-Driven Development

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—Write a lot of code —Work with other people —Write articles —Read books and code

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Write a lot of code —Lots of production code —Lots of throwaway code

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Collaborate —With people who are better than you —Or who aren't better than you

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Write Forces you to think.

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Learn your frameworks —Use Core Data —Use UITableViewController —Use NSURLSession

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Absolute Knowledge

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2014 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 1 2 3 4 5 Time How much I know

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Perceived Knowledge

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2014 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 1 2 3 4 5 Time How much I know

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Strive to become better

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Ship

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Writing better code —Quick wins —Value Objects —Lighter View Controllers

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Quick Wins

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I used to do this: if (buttonIndex == 0)

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I used to do this: if (buttonIndex == 0) instead, now I write if (buttonIndex == StartButton)

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I used to write this: if ([game state] == running || self.trainingMode)

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I used to write this: if ([game state] == running || self.trainingMode) Now I write this: BOOL shouldPauseGame = game.state == running || self.trainingMode; if (shouldPauseGame)

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Write small ﬁles I aim for 100-150 lines

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Write small ﬁles 325 ./THStyleSheet.m 279 THSkillboxView.m 263 THCardsViewController.m 243 THTimeLineView.m 221 THScreeningBarViewController.m 192 THEditPriorityViewController.m 185 User+Extensions.m 183 THScreenInstanceViewController.m 183 THRootViewController.m 179 THUserScreenInstancesController.m 168 THPriorityTimelineCollectionController.m 155 UIView+Extensions.m 155 NSArray+Extensions.m 154 THZoomingNavigationController.m

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Write small ﬁles find . -name "*.m" -exec wc -l "{}" \; | sort -n

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Use protocols instead of class inheritance They are much more ﬂexible and make for clearer code.

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Deep code paths - (void)alertView:(UIAlertView *)alertView didDismissWithButtonIndex:(NSInteger)buttonIndex { if (alertState == submitScore && game.score > 0) { // 20 lines if (result != nil && [resultKeys containsObject:@"position"] && [resultKeys containsObject:@"neededPoints"] && [resultKeys containsObject:@"deviceHighscore"] && [resultKeys

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Deep code paths Pull out things into separate, well-named methods

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Don't write fast code Optimize for readability

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Really learn Interface Builder This makes prototyping much faster

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Learn your frameworks

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What prevents me from using Core Data at this point is my concern for scalability and performance. It’s possible I’m just being thick-headed. — Brent Simmons, 27 Sep 2013

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So last weekend I switched from SQLite/FMDB to Core Data. This may come as a surprise. — Brent Simmons, 05 Oct 2013

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Core Data —Relationships —Batching —NSFetchedResultsController —Speed of use

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Value Objects

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I used NSDictionary for everything NSDate* birthDate = [NSDate dateWithTimeIntervalSince1970:131855*3600]; NSDictionary* person = @{ @"name": @"Chris", @"birthdate": birthDate, @"numberOfKids": @0 };

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Problems with NSDictionary —It's not typechecked —It might be mutated

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A ﬁrst step @interface Person : NSObject @property (nonatomic,copy) NSString* name; @property (nonatomic) NSDate* birthDate; @property (nonatomic) NSUInteger numberOfKids; @end

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Mutation Sometimes mutation is very handy. Most of the times it will bite you.

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@interface Person : NSObject @property (nonatomic,readonly) NSString* name; @property (nonatomic,readonly) NSDate* birthDate; @property (nonatomic,readonly) NSUInteger numberOfKids; - (instancetype) initWithName:(NSString*)name birthDate:(NSDate*)birthDate numberOfKids:(NSUInteger)numberOfKids; @end

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Value Objects —Use lots of them. —Make them immutable.

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Lighter View Controllers

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Keep your view controllers light This is the least reusable code you'll write

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What can you do? —Smarter views —Smarter models —Use view controller transitions —Use categories to populate views —Pull out protocols

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Use categories to populate views - (UITableViewCell*)tableView:(UITableView*)tv cellForRowAtIndexPath:(NSIndexPath*)ip { User *user = [self userAtIndexPath:ip]; MyCell *cell = [tv dequeueReusableCellWithIdentifier:ruI forIndexPath:ip]; cell.textLabel.text = user.name; cell.imageView.image = user.avatar; .... }

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Use categories to populate views @interface MyCell (ConfigureForUser) - (void)configureForUser:(User *)user; @end

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Use categories to populate views - (void)configureForUser:(User *)user { cell.textLabel.text = user.name; cell.imageView.image = user.avatar; ... }

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Use categories to populate views —Your view controller is a bit simpler —Your population code can be reused ... —But now your view knows about your model. Sort of.

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Pulling out protocols

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Pulling out protocols For example: UITableViewDataSource

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Creating a separate data source object @interface FetchedResultsControllerDataSource : NSObject

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Creating a separate data source object - (NSInteger)numberOfSectionsInTableView: (UITableView*)t { return self.fetchedResultsController.sections.count; }

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Creating a separate data source object - (NSInteger)tableView:(UITableView*)tableView numberOfRowsInSection:(NSInteger)sectionIndex { id section; section = self.frc.sections[sectionIndex]; return section.numberOfObjects; }

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Creating a separate data source object Working with the delegate - (UITableViewCell*)tableView:(UITableView*)tv cellForRowAtIndexPath:(NSIndexPath*)ip { id object = [self objectAtIndexPath:indexPath]; id cell = [tv dequeueReusableCellWithIdentifier:ruI forIndexPath:ip]; [self.delegate configureCell:cell withObject:object]; return cell; }

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Advantages of a separate data source —Lighter view controller —Testable —Reusable And you can do this for other protocols, too

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A separate data source —NSArrayDataSource —NSFRCollectionViewController —...

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So.... —Write for the person after you —Know your frameworks —Keep your view controllers light