diff options
Diffstat (limited to 'swift.html.markdown')
-rw-r--r-- | swift.html.markdown | 56 |
1 files changed, 28 insertions, 28 deletions
diff --git a/swift.html.markdown b/swift.html.markdown index c2fb3471..1f9fe897 100644 --- a/swift.html.markdown +++ b/swift.html.markdown @@ -91,7 +91,7 @@ let multiLineString = """ This is a multi-line string. It's called that because it takes up multiple lines (wow!) Any indentation beyond the closing quotation marks is kept, the rest is discarded. - You can include " or "" in multi-line strings because the delimeter is three "s. + You can include " or "" in multi-line strings because the delimiter is three "s. """ // Arrays @@ -159,12 +159,12 @@ let `class` = "keyword" or contains nil (no value) to indicate that a value is missing. Nil is roughly equivalent to `null` in other languages. A question mark (?) after the type marks the value as optional of that type. - + If a type is not optional, it is guaranteed to have a value. - + Because Swift requires every property to have a type, even nil must be explicitly stored as an Optional value. - + Optional<T> is an enum, with the cases .none (nil) and .some(T) (the value) */ @@ -178,7 +178,7 @@ let someOptionalString4 = String?.none //nil To access the value of an optional that has a value, use the postfix operator !, which force-unwraps it. Force-unwrapping is like saying, "I know that this optional definitely has a value, please give it to me." - + 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. @@ -194,7 +194,7 @@ if someOptionalString != nil { // Swift supports "optional chaining," which means that you can call functions // or get properties of optional values and they are optionals of the appropriate type. // You can even do this multiple times, hence the name "chaining." - + let empty = someOptionalString?.isEmpty // Bool? // if-let structure - @@ -370,7 +370,7 @@ func say(_ message: String) { } say("Hello") -// Default parameters can be ommitted when calling the function. +// Default parameters can be omitted when calling the function. func printParameters(requiredParameter r: Int, optionalParameter o: Int = 10) { print("The required parameter was \(r) and the optional parameter was \(o)") } @@ -443,7 +443,7 @@ func testGuard() { return // guard statements MUST exit the scope that they are in. // They generally use `return` or `throw`. } - + print("number is \(aNumber)") } testGuard() @@ -564,7 +564,7 @@ enum Furniture { case desk(height: Int) // Associate with String and Int case chair(String, Int) - + func description() -> String { //either placement of let is acceptable switch self { @@ -591,15 +591,15 @@ print(chair.description()) // "Chair of Foo with 40 cm" - Define initializers to set up their initial state - Be extended to expand their functionality beyond a default implementation - Conform to protocols to provide standard functionality of a certain kind - + Classes have additional capabilities that structures don't have: - Inheritance enables one class to inherit the characteristics of another. - Type casting enables you to check and interpret the type of a class instance at runtime. - Deinitializers enable an instance of a class to free up any resources it has assigned. - Reference counting allows more than one reference to a class instance. - + Unless you need to use a class for one of these reasons, use a struct. - + Structures are value types, while classes are reference types. */ @@ -607,7 +607,7 @@ print(chair.description()) // "Chair of Foo with 40 cm" struct NamesTable { let names: [String] - + // Custom subscript subscript(index: Int) -> String { return names[index] @@ -629,7 +629,7 @@ class Shape { class Rect: Shape { var sideLength: Int = 1 - + // Custom getter and setter property var perimeter: Int { get { @@ -640,16 +640,16 @@ class Rect: Shape { sideLength = newValue / 4 } } - + // 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) - + // 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` @@ -659,19 +659,19 @@ 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 -= 1 } } - + override func getArea() -> Int { return sideLength * sideLength } @@ -703,13 +703,13 @@ 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 } @@ -813,7 +813,7 @@ for _ in 0..<10 { - Internal: Accessible and subclassible in the module it is declared in. - Fileprivate: Accessible and subclassible in the file it is declared in. - Private: Accessible and subclassible in the enclosing declaration (think inner classes/structs/enums) - + See more here: https://docs.swift.org/swift-book/LanguageGuide/AccessControl.html */ @@ -878,11 +878,11 @@ extension Int { var doubled: Int { return self * 2 } - + func multipliedBy(num: Int) -> Int { return num * self } - + mutating func multiplyBy(num: Int) { self *= num } @@ -965,18 +965,18 @@ 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(value: 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(value: 7) - + do { // normal try operation that provides error handling via `catch` block try fakeFetch(value: 1) |