From 5dac348b72000dedc2e8a35f1ccaea55a7f408f7 Mon Sep 17 00:00:00 2001 From: Clayton Walker Date: Tue, 6 Oct 2015 23:00:11 -0400 Subject: [PATCH 1/3] Forgot to add myself as a contributor from swift-1 pull request. --- swift.html.markdown | 1 + 1 file changed, 1 insertion(+) diff --git a/swift.html.markdown b/swift.html.markdown index 509c9d2f..23ebcfc5 100644 --- a/swift.html.markdown +++ b/swift.html.markdown @@ -5,6 +5,7 @@ contributors: - ["Christopher Bess", "http://github.com/cbess"] - ["Joey Huang", "http://github.com/kamidox"] - ["Anthony Nguyen", "http://github.com/anthonyn60"] + - ["Clayton Walker", "https://github.com/cwalk"] filename: learnswift.swift --- From ad16a31c0751f244a46cadbfb3540943af73349d Mon Sep 17 00:00:00 2001 From: Clayton Walker Date: Tue, 6 Oct 2015 23:36:32 -0400 Subject: [PATCH 2/3] Added clearer description of Optionals and Unwrapping. Minor typo changes as well. --- swift.html.markdown | 43 +++++++++++++++++++++++++------------------ 1 file changed, 25 insertions(+), 18 deletions(-) diff --git a/swift.html.markdown b/swift.html.markdown index 23ebcfc5..46e5e6d4 100644 --- a/swift.html.markdown +++ b/swift.html.markdown @@ -58,8 +58,9 @@ let piText = "Pi = \(π), Pi 2 = \(π * 2)" // String interpolation print("Build value: \(buildValue)") // Build value: 7 /* - Optionals are a Swift language feature that allows you to store a `Some` or - `None` value. + Optionals are a Swift language feature that either contains a value, + or contains nil (no value) to indicate that a value is missing. + A question mark (?) after the type marks the value as optional. Because Swift requires every property to have a value, even nil must be explicitly stored as an Optional value. @@ -75,11 +76,17 @@ if someOptionalString != nil { if someOptionalString!.hasPrefix("opt") { print("has the prefix") } - + let empty = someOptionalString?.isEmpty } someOptionalString = nil +/* + To get the underlying type from an optional, you unwrap it using the + force unwrap operator (!). Only use the unwrap operator if you're sure + the underlying value isn't nil. +*/ + // implicitly unwrapped optional var unwrappedString: String! = "Value is expected." // same as above, but ! is a postfix operator (more syntax candy) @@ -94,13 +101,13 @@ if let someOptionalStringConstant = someOptionalString { // Swift has support for storing a value of any type. // AnyObject == id -// Unlike Objective-C `id`, AnyObject works with any value (Class, Int, struct, etc) +// Unlike Objective-C `id`, AnyObject works with any value (Class, Int, struct, etc.) var anyObjectVar: AnyObject = 7 anyObjectVar = "Changed value to a string, not good practice, but possible." /* Comment here - + /* Nested comments are also supported */ @@ -296,10 +303,10 @@ print(numbers) // [3, 6, 18] // MARK: Structures // -// Structures and classes have very similar capabilites +// Structures and classes have very similar capabilities struct NamesTable { let names = [String]() - + // Custom subscript subscript(index: Int) -> String { return names[index] @@ -330,7 +337,7 @@ public class Shape { internal class Rect: Shape { var sideLength: Int = 1 - + // Custom getter and setter property private var perimeter: Int { get { @@ -341,11 +348,11 @@ internal class Rect: Shape { sideLength = newValue / 4 } } - + // Lazily load a property // subShape remains nil (uninitialized) until getter called lazy var subShape = Rect(sideLength: 4) - + // If you don't need a custom getter and setter, // but still want to run code before and after getting or setting // a property, you can use `willSet` and `didSet` @@ -355,19 +362,19 @@ internal class Rect: Shape { print(someIdentifier) } } - + init(sideLength: Int) { self.sideLength = sideLength // always super.init last when init custom properties super.init() } - + func shrink() { if sideLength > 0 { --sideLength } } - + override func getArea() -> Int { return sideLength * sideLength } @@ -399,13 +406,13 @@ class Circle: Shape { override func getArea() -> Int { return 3 * radius * radius } - + // Place a question mark postfix after `init` is an optional init // which can return nil init?(radius: Int) { self.radius = radius super.init() - + if radius <= 0 { return nil } @@ -459,7 +466,7 @@ enum Furniture { case Desk(height: Int) // Associate with String and Int case Chair(String, Int) - + func description() -> String { switch self { case .Desk(let height): @@ -498,7 +505,7 @@ protocol ShapeGenerator { class MyShape: Rect { var delegate: TransformShape? - + func grow() { sideLength += 2 @@ -533,7 +540,7 @@ extension Int { var customProperty: String { return "This is \(self)" } - + func multiplyBy(num: Int) -> Int { return num * self } From b4860de42f2bbf0ab97ef28085eb40accb030657 Mon Sep 17 00:00:00 2001 From: Clayton Walker Date: Thu, 8 Oct 2015 23:27:19 -0400 Subject: [PATCH 3/3] Suggested changes --- swift.html.markdown | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/swift.html.markdown b/swift.html.markdown index 46e5e6d4..9f0019d8 100644 --- a/swift.html.markdown +++ b/swift.html.markdown @@ -58,8 +58,8 @@ let piText = "Pi = \(π), Pi 2 = \(π * 2)" // String interpolation print("Build value: \(buildValue)") // Build value: 7 /* - Optionals are a Swift language feature that either contains a value, - or contains nil (no value) to indicate that a value is missing. + Optionals are a Swift language feature that either contains a value, + or contains nil (no value) to indicate that a value is missing. A question mark (?) after the type marks the value as optional. Because Swift requires every property to have a value, even nil must be @@ -82,9 +82,9 @@ if someOptionalString != nil { someOptionalString = nil /* - To get the underlying type from an optional, you unwrap it using the - force unwrap operator (!). Only use the unwrap operator if you're sure - the underlying value isn't nil. + Trying to use ! to access a non-existent optional value triggers a runtime + error. Always make sure that an optional contains a non-nil value before + using ! to force-unwrap its value. */ // implicitly unwrapped optional