A Swift Approach - Speaker Deck

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A SWIFT APPROACH

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NEW CONCEPTS

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RUNTIME

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@objc / NSObject

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RUNTIME

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WWDC 2015

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OPTIONALS?

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func compute() -> Bool?

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true false neither

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LACK OF A VALUE

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NOT AN EMPTY VALUE

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CAN'T WE DO THIS IN OBJECTIVE-C?

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nil Nil NULL CGRectNull -1 0 NSNotFound NSNull ...

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EXPRESS YOU DON'T ACCEPT NIL

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EXPRESS YOU WILL NOT RETURN NIL

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/// You **MUST** pass in a URL - (instancetype)initWithURL:(NSURL *)URL { NSParameterAssert(URL != nil); }

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- (UITableViewCell *)tableView:(UITableView *)tv cellForRowAtIndexPath:(NSIndexPath *)path { return nil; }

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No content

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RUNTIME ERROR

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RUNTIME ERROR

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COMPILE ERROR

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TUPLES

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PYTHON

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func get(username:String) -> (Person?, NSError?)

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let person, error = get("Kyle")

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OBJECTIVE-C

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NSError *error; Person *person = [Person getPerson:@"Kyle" error:&error];

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NAMED TUPLES

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func get(username:String) -> (person:Person?, error:NSError?)

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let result = get("Kyle") result.person result.error

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- (NSArray *)getPerson:(NSString *)username; - (NSDictionary *)getPerson:(NSString *)username;

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NSDictionary *components = [Person getPerson:@"kyle"]; Person *person = components["person"]; NSError *error = components["error"];

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TYPE SAFETY?

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FRAGILE

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CLOSURES

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EVERYTHING IS A CLOSURE

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class TestObject { func testA() -> () { println("first test") } var testB:(() -> ()) = { println("second test") } }

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let testing = TestObject() testing.testA() testing.testB()

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testing.testB = testing.testA

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testing.testB() // Actually calls testA

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CONSISTENCY

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GENERICS

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func max(a:T, b:T) -> T { return a > b ? a : b }

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max(anInteger, anotherInteger) max(aFloat, anotherFloat) max(aString, anotherString)

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PATTERN MATCHING

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let point = (1, 2) switch point { case (0, 0): println("(0, 0) is at the origin.") case (-2...2, -2...2): println("(\(point.0), \(point.1)) is near the origin.") default: println("The point is at (\(point.0), \(point.1)).") } // prints "(1, 2) is near the origin."

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@auto_closure

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delay(5, println("Hello World"))

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func delay(time:UInt32, block:@auto_closure) { sleep(time) block() }

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BUILDING ASSERT() IN SWIFT

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assert(someExpensiveComputation() != 42)

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func assert(predicate : () -> Bool) { #if !NDEBUG if !predicate() { abort() } #endif }

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PLAYGROUNDS

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PLAYGROUNDS

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SWIFT

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SAFER

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CONVENTIONS

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CONVENTIONS

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LANGUAGE CONSTRAINTS

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BETTER CODE

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BETTER DEVELOPERS

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LESS BUGS

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WE'RE ALL BEGINNERS

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No content

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"I DON'T KNOW IF IT'S A BUG OR I'M DOING IT WRONG" ASH FURROW

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FILE RADARS

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SHAPE

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APPLE WILL break YOUR CODE

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FOR GOOD, NOT EVIL

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XCODE 6 GM?

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"WE EXPECT TO LOCK THIS DOWN"

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"BUT NOT BY THE FINAL RELEASE OF SWIFT THIS FALL."

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EARLY

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FUTURE

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COMMON PATTERNS

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