iOS Development for Java Developers

Introduction to iOS Development and Objective-C, slated towards Java programmers. Provides some examples of common constructs in Java syntax and their Objective-C counterparts.
Shows some "weird" language and platform features that are foreign to most people primarily living and thinking in Java.

Sample application on GitHub at https://github.com/dschneller/CodingSerbia as a coding demo, showing some of the features presented and demoing the use of table view controllers and the MVC pattern in general.

Transcript

1. iOS$Programming For$Java$Developers Daniel$Schneller codecentric$AG @dschneller
2. Agenda •iOS$–$What$is$it,$anyway? •Tooling •ObjecDveEC$First$Steps •ObjecDveEC$“Bag$of$tricks” •Coding$Demo •Recap
3. iOS$–$What$is$it,$ anyway?
4. iOS$–$What$is$it,$anyway? •Originally$iPhoneOS$(2007),$iOS$since$2010 •BSD$variant,$based$on$“Darwin”$Mach$ Kernel •Strong$resemblance$to$OS$X •Full$preempDve$mulDEtasking •32$&$64$bit$(iPhone$5s)
5. •Runs$on$iPhone,$iPod$Touch,$iPad,$AppleTV •Development$happens$on$OS$X •Devices$based$on$ARM$CPU$architecture •Tools$employ$cross$compilaDon$from$Macs •“Stripped$down”$version$of$iOS$for$x86$in$ the$iOS$Simulator iOS$–$What$is$it,$anyway?
6. Tooling
7. Xcode (poor$man’s$Eclipse) •Apple’s$standard$IDE •Code$EdiDng •UI$Design •(Version$Control) •Build$&$Deployment
8. Xcode
9. iOS$Simulator •Runs$iOS$on$the$ desktop •iPhone$and$iPad •SimulaDon,$not$ emulaDon •Limited,$but$useful
10. Instruments •Simulator$&$Device •Memory •CPU •Graphics •IO
11. ObjecDveEC First$Steps
12. ObjecDveEC •Superset$of$C$(like$C++) •Object$Oriented$AddiDons •Dynamically$Typed •Driven$by$the$ObjC$runDme •AcDvely$evolving$(“ObjC$2.0”) •“Strange”$Syntax
13. Key$Differences$to$Java •(SemiE)manual$memory$management •Real$pointers$(it’s$C$ager$all) •No$enforced$namespaces/packages •Some$“modern”$features$like$blocks$ (closures),$collecDon$literals,$properDes •ExcepDons$present,$but$rarely$used
14. Mapping$Java$to$ObjC Java Objective C int x = 5; int x = 5; boolean flag = true; boolean flag = false; BOOL flag = YES; // or != 0 BOOL flag = NO; // or == 0 Object o = null; id o = nil; map.put(“key”, “value”); dict[@”key”] = @”value”
15. Mapping$Java$to$ObjC Java Objective C class Child extends Parent @interface Child : Parent @implementation Child interface TableViewDelegate @protocol TableViewDelegate class C implements I @interface C <I> @implementation C abstract class AbstractClass only by convention
16. Mapping$Java$to$ObjC Java Objective C package com.codingserbia class MyClass CDSMyClass void instanceMethod() - (void) instanceMethod static int staticMethod() + (int) classMethod
17. Mapping$Java$to$ObjC Java Objective C String s = “Hello, World” NSString* s = @”Hello, World” s = s.toUpperCase(); s = [s upperCaseString]; Object o = this.a().b(3).c(true) id o = [[[self a] b:3] c:YES] MyClass m = new MyClass(); MyClass* m = [[MyClass alloc] init]; c = new Captain(“Kirk”, “Jim”, 7); c = [Captain alloc] initWithLastname:@”Kirk” firstName:@”Jim” playedInMovies:7];
18. ObjecDveEC
19. No$NullPointerExcepDons •Sending$messages$to$‘nil’$references$is$ok •No$excepDons$thrown •Just$return$‘nil’$again •Allows$convenient$call$chaining •Used$extensively$throughout$the$libraries
20. No$NullPointerExcepDons String firstLowerCaseString(List x) { if (x == null) { return null; } else if (x.size() == 0) { return null; } else { Object o = x.get(0); if (x == null) { return null; } return x.toString().toLowerCase(); } }
21. No$NullPointerExcepDons - (NSString*) firstLowerCaseString:(NSArray*)x { return [[[x firstObject] description] lowercaseString]; }
22. OpDonal$protocol$methods •Great$for$delegate/callback$based$APIs •Callers$must$check$at$runDme,$if$they$are$ implemented$on$the$called$object •Used$pervasively$throughout$frameworks @protocol UITableViewDataSource<NSObject> @optional - (NSString *)tableView:(UITableView*)tableView titleForHeaderInSection:(NSInteger)section; - (NSString *)tableView:(UITableView*)tableView titleForFooterInSection:(NSInteger)section; @end
23. Categories •Extend$classes$at$runDme •New$methods$even$on$framework$classes •Great$for$decoupling @implementation NSNumber (CDSHumanReadable) - (NSString*)humanReadableFilesize { NSByteCountFormatter* formatter = [[NSByteCountFormatter alloc] init]; return [formatter stringFromByteCount:[self longLongValue]]; } @end
24. Categories •Extend$classes$at$runDme •New$methods$even$on$framework$classes •Great$for$decoupling @implementation NSNumber (CDSHumanReadable) - (NSString*)humanReadableFilesize { NSByteCountFormatter* formatter = [[NSByteCountFormatter alloc] init]; return [formatter stringFromByteCount:[self longLongValue]]; } @end @interface NSDictionary (RKAdditions) - (NSString *)stringWithURLEncodedEntries; @end
25. Method$‘swizzling’ •Replace$implementaDons$at$runDme •Similar$to$Categories,$but$provides$access$ to$the$original$method$implementaDon •Allows$changing$the$behavior$of$otherwise$ inaccessible$implementaDons
26. Method$‘swizzling’ •Give$all$views$a$border$for$debugging$by$ amending$UIView$constructors$appEwide @implementation UIView (CDSBorder) - (id)swzld_initWithFrame:(CGRect)frame { // Call original implementation id result = [self swzld_initWithFrame:frame]; if ([result respondsToSelector:@selector(layer)]) { // Get layer for this view. CALayer *layer = [result layer]; // Set border on layer. layer.borderWidth = 2; layer.borderColor = [[UIColor redColor] CGColor]; } // Return the modified view. return result; } + (void)load { Method original, swizzle; // Get the "- (id)initWithFrame:" method. original = class_getInstanceMethod(self, @selector(initWithFrame:)); // Get the "- (id)swzld_initWithFrame:" method. swizzle = class_getInstanceMethod(self, @selector(swzld_initWithFrame:)); // Swap their implementations. method_exchangeImplementations(original, swizzle); }
27. Method$‘swizzling’
28. Method$‘swizzling’ •Powerful,$but$not$for$the$faint$of$heart •Enables$advanced$features$and$frameworks •Also$enables$advanced$bugs$;) •Be$careful$not$break$promises$the$original$ implementaDon$makes
29. [Coding Demo]; Sample$App$available$at https://github.com/dschneller/CodingSerbia
30. Recap •Quickly$get$first$results •Not$so$quickly$get$really$proficient •Xcode$editor$a$bit$lacking •Great$Frameworks •MVC$everywhere •Biggest$hinderance:$You$need$a$Mac
31. github.com/dschneller daniel.schneller@codecentric.de $$$$$@dschneller hrp://www.danielschneller.de Thank$you! QuesDons?
32. You$have$reached$the$end$of$the$universe. There$is$nothing$more$to$see.$Go$home$now. Or$listen$to$some$other$talk.