Emerging Best Practices in Swift

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Emerging Best Practices in Swift Ash Furrow

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No content

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I was Afraid That we'd just write Objective-C in Swift syntax.

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Everything turned out Fine

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Today, we're exploring best practices in Swift.

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We've been here before. Swift 2 is significantly different. Always be learning.

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Let's Go

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Those who don't know history are doomed to repeat it. — Lots of people.

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Wrong.

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Those who don't know the past can't make informed decisions about the present. — Me

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iOS 5 or Earlier? Let's see a show of hands.

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Before Object Literals NSArray *array = [NSArray arrayWithObjects: @"This", @"is", @"so", @"tedious", nil]; NSDictionary *dictionary = [NSDictionary dictionaryWithObjectsAndKeys: @"Who would do this?", @"Not me", nil]; NSNumber *number = [NSNumber numberWithInt: 401];

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Before Object Literals and ARC NSArray *array = [[NSArray arrayWithObjects: @"This", @"is", @"so", @"tedious", nil] retain]; NSDictionary *dictionary = [[NSDictionary dictionaryWithObjectsAndKeys: @"Who would do this?", @"Not me", nil] retain]; NSNumber *number = [[NSNumber numberWithInt: 401] retain];

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After Object Literals NSArray *array = @[ @"This", @"is", @"much", @"better" ]; NSDictionary *dictionary = @{ @"Who likes this?": @"Me!" }; NSNumber *number = @(401);

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Adopted immediately. Clearly better. Became a best practice.

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Blocks — iOS 4 introduced blocks and GCD. — Adopted... eventually. — Required new ideas. — Became a best practice.

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Blocks — iOS 4 introduced blocks and GCD. — Adopted... eventually. — Required new ideas. — Became a best practice. — Blocks now enable other best practices.

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Swift 2

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Swift 2 — Lots of new syntax. — New syntax lets us do cool new things. — Like blocks, syntax is only a tool.

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Swift 2 — guard — defer — throws — etc...

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Should I use guard?

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What can I do with guard?

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Examples

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If Overload if let thing = optionalThing { if thing.shouldDoThing { if let otherThing = thing.otherThing { doStuffWithThing(otherThing) } } }

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where to the rescue if let thing = optionalThing, let otherThing = thing.otherThing where thing.shoudDoThing { doStuffWithThing(otherThing) }

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where to the rescue if let thing = optionalThing, let otherThing = thing.otherThing where thing.shoudDoThing { doStuffWithThing(otherThing) } if...where isn't cool. You know what's cool?

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where to the rescue if let thing = optionalThing, let otherThing = thing.otherThing where thing.shoudDoThing { doStuffWithThing(otherThing) } if...where isn't cool. You know what's cool? ... Neither do I. Let's look together!

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Avoid mutability func strings(parameter: [String], startingWith prefix: String) -> [String] { var mutableArray = [String]() for string in parameter { if string.hasPrefix(prefix) { mutableArray.append(string) } } return mutableArray }

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Avoid mutability func strings(parameter: [String], startingWith prefix: String) -> [String] { return parameter.filter { $0.hasPrefix(prefix) } }

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Extract associated values 1. Use Swift enums. 2. Attach associated values. 3. Extract using case.

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Extract associated values enum Result { case Success(T) case Failure(reason: String) } ... switch doThing() { case .Success: print("!") case .Failure(let reason): print("Oops: \(reason)") }

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Extract associated values if case .Success = doThing() { print("!") }

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That's all just syntax.

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Protocol-Oriented Programming

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Just go watch the WWDC video.

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Syntax itself is not a best practice. The patterns enabled by syntax are what really matter. We need to discover them.

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Learning !

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Learning shouldn't just happen during the Xcode betas.

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Learning is a constant activity, a state of mind.

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Learning — Look for code smells. — Ask yourself how you'd solve something differently. — Pick a Swift feature, ask "what could I do with this?" — Be comfortable throwing code away.

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What about other communities? I bet they have good ideas, too...

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You should write a Blog

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Wrap-up

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We have a history of being awesome, let's keep it up. Re-evaluate solutions to familiar problems. Always be learning. Also, write a blog.

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Make better mistakes tomorrow.