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-rw-r--r--swift.html.markdown155
1 files changed, 111 insertions, 44 deletions
diff --git a/swift.html.markdown b/swift.html.markdown
index f3746613..33ff8451 100644
--- a/swift.html.markdown
+++ b/swift.html.markdown
@@ -32,7 +32,7 @@ import UIKit
// In Swift 2, println and print were combined into one print method. Print automatically appends a new line.
print("Hello, world") // println is now print
-print("Hello, world", appendNewLine: false) // printing without appending a newline
+print("Hello, world", terminator: "") // printing without appending a newline
// variables (var) value can change after being set
// constants (let) value can NOT be changed after being set
@@ -60,14 +60,14 @@ 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.
- A question mark (?) after the type marks the value as optional.
+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.
+Because Swift requires every property to have a value, even nil must be
+explicitly stored as an Optional value.
- Optional<T> is an enum.
+Optional<T> is an enum.
*/
var someOptionalString: String? = "optional" // Can be nil
// same as above, but ? is a postfix operator (syntax candy)
@@ -84,9 +84,9 @@ if someOptionalString != nil {
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.
+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
@@ -120,8 +120,8 @@ anyObjectVar = "Changed value to a string, not good practice, but possible."
//
/*
- Array and Dictionary types are structs. So `let` and `var` also indicate
- that they are mutable (var) or immutable (let) when declaring these types.
+Array and Dictionary types are structs. So `let` and `var` also indicate
+that they are mutable (var) or immutable (let) when declaring these types.
*/
// Array
@@ -149,6 +149,14 @@ var explicitEmptyMutableDictionary: [String: Float] = [:] // same as above
// MARK: Control Flow
//
+// Condition statements support "where" clauses, which can be used
+// to help provide conditions on optional values.
+// Both the assignment and the "where" clause must pass.
+let someNumber = Optional<Int>(7)
+if let num = someNumber where num > 3 {
+ print("num is greater than 3")
+}
+
// for loop (array)
let myArray = [1, 1, 2, 3, 5]
for value in myArray {
@@ -178,8 +186,8 @@ while i < 1000 {
i *= 2
}
-// do-while loop
-do {
+// repeat-while loop
+repeat {
print("hello")
} while 1 == 2
@@ -198,7 +206,6 @@ default: // required (in order to cover all possible input)
let vegetableComment = "Everything tastes good in soup."
}
-
//
// MARK: Functions
//
@@ -209,25 +216,25 @@ default: // required (in order to cover all possible input)
// Function with Swift header docs (format as reStructedText)
/**
- A greet operation
+A greet operation
- - A bullet in docs
- - Another bullet in the docs
+- A bullet in docs
+- Another bullet in the docs
- :param: name A name
- :param: day A day
- :returns: A string containing the name and day value.
+:param: name A name
+:param: day A day
+:returns: A string containing the name and day value.
*/
func greet(name: String, day: String) -> String {
return "Hello \(name), today is \(day)."
}
-greet("Bob", "Tuesday")
+greet("Bob", day: "Tuesday")
// similar to above except for the function parameter behaviors
-func greet2(#requiredName: String, externalParamName localParamName: String) -> String {
+func greet2(requiredName requiredName: String, externalParamName localParamName: String) -> String {
return "Hello \(requiredName), the day is \(localParamName)"
}
-greet2(requiredName:"John", externalParamName: "Sunday")
+greet2(requiredName: "John", externalParamName: "Sunday")
// Function that returns multiple items in a tuple
func getGasPrices() -> (Double, Double, Double) {
@@ -240,11 +247,33 @@ let (_, price1, _) = pricesTuple // price1 == 3.69
print(price1 == pricesTuple.1) // true
print("Gas price: \(price)")
+// Labeled/named tuple params
+func getGasPrices2() -> (lowestPrice: Double, highestPrice: Double, midPrice: Double) {
+ return (1.77, 37.70, 7.37)
+}
+let pricesTuple2 = getGasPrices2()
+let price2 = pricesTuple2.lowestPrice
+let (_, price3, _) = pricesTuple2
+print(pricesTuple2.highestPrice == pricesTuple2.1) // true
+print("Highest gas price: \(pricesTuple2.highestPrice)")
+
+// guard statements
+func testGuard() {
+ // guards provide early exits or breaks, placing the error handler code near the conditions.
+ // it places variables it declares in the same scope as the guard statement.
+ guard let aNumber = Optional<Int>(7) else {
+ return
+ }
+
+ print("number is \(aNumber)")
+}
+testGuard()
+
// Variadic Args
func setup(numbers: Int...) {
// its an array
- let number = numbers[0]
- let argCount = numbers.count
+ let _ = numbers[0]
+ let _ = numbers.count
}
// Passing and returning functions
@@ -265,7 +294,7 @@ func swapTwoInts(inout a: Int, inout b: Int) {
}
var someIntA = 7
var someIntB = 3
-swapTwoInts(&someIntA, &someIntB)
+swapTwoInts(&someIntA, b: &someIntB)
print(someIntB) // 7
@@ -293,23 +322,17 @@ numbers = numbers.map({ number in 3 * number })
print(numbers) // [3, 6, 18]
// Trailing closure
-numbers = sorted(numbers) { $0 > $1 }
+numbers = numbers.sort { $0 > $1 }
print(numbers) // [18, 6, 3]
-// Super shorthand, since the < operator infers the types
-
-numbers = sorted(numbers, < )
-
-print(numbers) // [3, 6, 18]
-
//
// MARK: Structures
//
// Structures and classes have very similar capabilities
struct NamesTable {
- let names = [String]()
+ let names: [String]
// Custom subscript
subscript(index: Int) -> String {
@@ -323,6 +346,44 @@ let name = namesTable[1]
print("Name is \(name)") // Name is Them
//
+// MARK: Error Handling
+//
+
+// The `ErrorType` protocol is used when throwing errors to catch
+enum MyError: ErrorType {
+ case BadValue(msg: String)
+ case ReallyBadValue(msg: String)
+}
+
+// functions marked with `throws` must be called using `try`
+func fakeFetch(value: Int) throws -> String {
+ guard 7 == value else {
+ throw MyError.ReallyBadValue(msg: "Some really bad value")
+ }
+
+ return "test"
+}
+
+func testTryStuff() {
+ // assumes there will be no error thrown, otherwise a runtime exception is raised
+ let _ = try! fakeFetch(7)
+
+ // if an error is thrown, then it proceeds, but if the value is nil
+ // it also wraps every return value in an optional, even if its already optional
+ let _ = try? fakeFetch(7)
+
+ do {
+ // normal try operation that provides error handling via `catch` block
+ try fakeFetch(1)
+ } catch MyError.BadValue(let msg) {
+ print("Error message: \(msg)")
+ } catch {
+ // must be exhaustive
+ }
+}
+testTryStuff()
+
+//
// MARK: Classes
//
@@ -353,6 +414,11 @@ internal class Rect: Shape {
}
}
+ // Computed properties must be declared as `var`, you know, cause' they can change
+ var smallestSideLength: Int {
+ return self.sideLength - 1
+ }
+
// Lazily load a property
// subShape remains nil (uninitialized) until getter called
lazy var subShape = Rect(sideLength: 4)
@@ -457,9 +523,10 @@ enum Suit {
// when the variable is explicitly declared
var suitValue: Suit = .Hearts
-// Non-Integer enums require direct raw value assignments
+// String enums can have direct raw value assignments
+// or their raw values will be derived from the Enum field
enum BookName: String {
- case John = "John"
+ case John
case Luke = "Luke"
}
print("Name: \(BookName.John.rawValue)")
@@ -503,7 +570,7 @@ protocol ShapeGenerator {
// Protocols declared with @objc allow optional functions,
// which allow you to check for conformance
@objc protocol TransformShape {
- optional func reshaped()
+ optional func reshape()
optional func canReshape() -> Bool
}
@@ -516,9 +583,9 @@ class MyShape: Rect {
// Place a question mark after an optional property, method, or
// subscript to gracefully ignore a nil value and return nil
// instead of throwing a runtime error ("optional chaining").
- if let allow = self.delegate?.canReshape?() {
+ if let reshape = self.delegate?.canReshape?() where reshape {
// test for delegate then for method
- self.delegate?.reshaped?()
+ self.delegate?.reshape?()
}
}
}
@@ -530,8 +597,8 @@ class MyShape: Rect {
// `extension`s: Add extra functionality to an already existing type
-// Square now "conforms" to the `Printable` protocol
-extension Square: Printable {
+// Square now "conforms" to the `CustomStringConvertible` protocol
+extension Square: CustomStringConvertible {
var description: String {
return "Area: \(self.getArea()) - ID: \(self.identifier)"
}
@@ -556,8 +623,8 @@ print(14.multiplyBy(3)) // 42
// Generics: Similar to Java and C#. Use the `where` keyword to specify the
// requirements of the generics.
-func findIndex<T: Equatable>(array: [T], valueToFind: T) -> Int? {
- for (index, value) in enumerate(array) {
+func findIndex<T: Equatable>(array: [T], _ valueToFind: T) -> Int? {
+ for (index, value) in array.enumerate() {
if value == valueToFind {
return index
}