Emerging Best Practices in Swift

Presented at iOSoho: http://www.meetup.com/iOSoho/events/224796318/

Transcript

1. Emerging Best Practices in
   Swift
   Ash Furrow
   

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

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4. Everything turned out
   Fine
   

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5. Today, we're exploring best
   practices in Swift.
   

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

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7. Let's Go
   

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

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9. Wrong.
   

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

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

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12. 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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13. 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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14. !
    

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

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16. Adopted immediately.
    Clearly better.
    Became a best practice.
    

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

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18. 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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19. Swift 2
    

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

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22. Should I use guard?
    

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23. What can I do with guard?
    

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24. Examples
    

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

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

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27. 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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28. 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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29. 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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30. 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
    }
    That's silly.
    

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

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

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

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35. That's all just syntax.
    

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36. Protocol-Oriented
    Programming
    

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37. Just go watch the WWDC video.
    

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38. 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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39. Learning
    !
    

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40. Learning shouldn't just
    happen during the Xcode
    betas.
    

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41. Learning is a constant
    activity, a state of mind.
    

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

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44. You should write a
    Blog
    

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45. Wrap-up
    

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46. 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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47. Make better
    mistakes tomorrow.
    

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