NSHipster New Year's 2016

nshipster-new-years-2016.md

Greetings and salutations, NSHipsters!

As the year winds down, it's a tradition here at NSHipster to ask you, dear readers, to offer up your favorite tricks and tips from the past year as gifts to your fellow hipsters. With iOS 9, El Capitan, brand new watch- and tvOS's, and the open-sourcing of some minor Apple-related tech, there's bound to be lots to share.

Submit your favorite piece of Swift or @objc trivia, helpful hints, unexpected discoveries, useful workarounds, useless fascinations, or anything else you found cool this year. Just comment below!

If you need inspiration, try the list from last year, or from the year before, or from the year before that.

새해 복 많이 받으세요! 🎆

The addition of the where clause has made my code simple and compact while remaining readable. In addition, it has a broad application in Swift, so that it can be applied in nearly any kind of control-flow statement, such as for loop, while loop, if, guard, switch, and even in extension declarations. One simple way I like to use it is in my prepareForSegue method:

if let segueID = segue.identifier where segueID == "mySegue" {
    ...
}

The combo of unwrapping and performing a condition check is most commonly where I use the where clause. The where clause is not going to change your life, but it should be an easy and useful addition to your Swift skills.

Additional type safety with phantom types:

struct Kilometer {}
struct Meter {}

struct DistanceT<T> {
    private let value: Int

    init(value: Int) {
        self.value = value
    }
}

func +<T>(left: DistanceT<T>, right: DistanceT<T>) -> DistanceT<T> {
    return DistanceT(value: left.value + right.value)
}

extension Int {
    var km: DistanceT<Kilometer> {
        return DistanceT<Kilometer>(value: self)
    }
    var m: DistanceT<Meter> {
        return DistanceT<Meter>(value: self)
    }
}


let distanceKilometers = 5.km
let distanceMeters = 15.m
let newDistance = distanceKilometers + distanceKilometers // Ok
let newDistance = distanceKilometers + distanceMeters // Compiler error

This was a good one from @kyleve - https://gist.github.com/kyleve/90c889e584b9af6256ae

How to tell if your app is running under UI Tests:

UI Tests:

class UITests: TestCase {
    let app = XCUIApplication()

    override func setUp() {
        super.setUp()
        app.launchArguments = ["UI-TESTING"]
        app.launch()
    }
}

App Code:

func UITesting() -> Bool {
    return NSProcessInfo.processInfo().arguments.contains("UI-TESTING")
}