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-rw-r--r--swift.html.markdown60
1 files changed, 41 insertions, 19 deletions
diff --git a/swift.html.markdown b/swift.html.markdown
index 86a0b89a..f451288d 100644
--- a/swift.html.markdown
+++ b/swift.html.markdown
@@ -3,8 +3,9 @@ language: swift
contributors:
- ["Grant Timmerman", "http://github.com/grant"]
- ["Christopher Bess", "http://github.com/cbess"]
- - ["Joey Huang", "http://github.com/kamidox"]
+ - ["Joey Huang", "http://github.com/kamidox"]
- ["Anthony Nguyen", "http://github.com/anthonyn60"]
+ - ["Clayton Walker", "https://github.com/cwalk"]
filename: learnswift.swift
---
@@ -57,8 +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.
@@ -74,11 +76,17 @@ if someOptionalString != nil {
if someOptionalString!.hasPrefix("opt") {
print("has the prefix")
}
-
+
let empty = someOptionalString?.isEmpty
}
someOptionalString = 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
var unwrappedString: String! = "Value is expected."
// same as above, but ! is a postfix operator (more syntax candy)
@@ -93,13 +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
*/
@@ -295,10 +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]
@@ -329,7 +337,7 @@ public class Shape {
internal class Rect: Shape {
var sideLength: Int = 1
-
+
// Custom getter and setter property
private var perimeter: Int {
get {
@@ -340,11 +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`
@@ -354,19 +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
}
@@ -398,13 +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
}
@@ -458,7 +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):
@@ -497,7 +505,7 @@ protocol ShapeGenerator {
class MyShape: Rect {
var delegate: TransformShape?
-
+
func grow() {
sideLength += 2
@@ -532,7 +540,7 @@ extension Int {
var customProperty: String {
return "This is \(self)"
}
-
+
func multiplyBy(num: Int) -> Int {
return num * self
}
@@ -574,4 +582,18 @@ print(mySquare.sideLength) // 4
// change side length using custom !!! operator, increases size by 3
!!!mySquare
print(mySquare.sideLength) // 12
+
+// Operators can also be generics
+infix operator <-> {}
+func <-><T: Equatable> (inout a: T, inout b: T) {
+ let c = a
+ a = b
+ b = c
+}
+
+var foo: Float = 10
+var bar: Float = 20
+
+foo <-> bar
+print("foo is \(foo), bar is \(bar)") // "foo is 20.0, bar is 10.0"
```