LS01 - Swift Intro part 1 PDF

COMP228 App Development Session: 2024-2025 Lecture Set 1 - Swift Introduction Phil Jimmieson - Department of Computer Science [ last updated: 19th Sept 2024 ] 1  COMP228 App Development...

COMP228 App Development Session: 2024-2025 Lecture Set 1 - Swift Introduction Phil Jimmieson - Department of Computer Science [ last updated: 19th Sept 2024 ] 1  COMP228 App Development Session: 2024-2025 Lecture Set 1 - Swift Introduction - part 1 Phil Jimmieson - Department of Computer Science [ last updated: 19th Sept 2024 ] 2  In these Slides... We will cover: Introduction to Swift 5.9 Swift Basics / Language Intro Classes and Structures Method Syntax Message Passing Memory Management A quick look at the Foundation Framework An introduction to the framework 3 Swift Introduction 4  What is Swift? An object-oriented language “Objective C without the C” Developed originally by Chris Lattner at Apple Open Source as of Dec 2015 Employs modern language theory concepts Exploits a number of object oriented principles Inherits many principles (but not syntax) from Smalltalk Objective C Aim is to simplify iOS programming. Concatenating two Unicode strings NSString *str = @"hello,"; str = [str stringByAppendingString:@" world"]; Swift var str = "hello," equivalent str = str + " world" 5  Swift Basics Swift version 4.0 - released September 2017 some Swift 3 features deprecated and some earlier Swift features removed Swift version 4.2 - released September 2018 minor updates to version 4.1 Swift 5.0 - released February 2019 ABI Compatibility on Apple platforms (all subsequent releases can rely on OS Swift runtime and standard library) Swift 5.1- released September 2019 Module stability - developers can make changes to their libraries without necessarily breaking binary compatibility. Swift 5.2 - released March 2020 focused on “improving the developer experience” 6  Swift Basics Swift 5.3 - released September 2020 (in Xcode 12) (mostly) additional features to support SwiftUI Swift 5.4 - released April 2021 (in Xcode 12.1) faster build performance, faster code completion Swift 5.5 - released September 2021 (in Xcode 13) support for asynchronous code - async / await Swift 5.6 - released March 2022 Package manager improvements Swift 5.7 - September 2022 (in Xcode 14) Regex literals and a RegexBuilder library. If-let shorthand 7  Swift Basics Swift 5.8 - released March 2023 Adds a new StaticBigInt type and tidies up some inconsistencies in the language Swift 5.9 - 18th Septeber 2023 Macros. Non-copyable types. Swift 6 - Released in September 2024 Cross-platform APIs. C++ interoperability. Data race safety checks. Foundation framework rewritten in Swift 8  Swift Language Intro part 1 Standard Types Tuples Strings 9 Standard Types 10  Swift Language Intro - part 1 Constants and variables use standard naming scheme (start with lowercase letter and camel case) let myString = "The weather looks like rain” var coreTemperature = 36.9 //inferred by the compiler to be a Double var myInt: Int Constants declared with let, Variables with var types can be inferred from default values (else you’ll need to specify them). No “;” needed on the end of a line. 11  Swift Language Intro - part 1 Ints obviously Swift has an integer type: var myInt = 97 But as a convenience, when declared, large integers can include the “_” character inserted into them to aid readability var speedOfLight = 186_000 //miles per second var populationOfUK = 66_040_200 //in 2017 ( If you print these, the _ does not appear in the output ) 12  Swift Language Intro - part 1 Standard types: String, Double, Int (+ related e.g. UInt, UInt32, Int32, StaticBigInt, Float16) Bool = “true” or “false” 13  Swift Language Intro - part 1 Generating random Ints in Swift < 4.2 involved the use of a UInt32 via arc4random_uniform() let diceRoll = arc4random_uniform(6) + 1 //value between 1 and 6 Swift 4.2 added a cryptographically secure randomiser to Swift for use in the numeric types. let diceRoll = Int.random(in: 1...6) //value between 1 and 6 This is typical of how the aim of many of the improvements to Swift - to simplify and make your code clearer. 14 Tuples 15  Swift Language Intro - part 1 Tuples (multiple values grouped into a single value) let http404Error = (404, "Not Found") // http404Error is of type (Int, String), and equals (404, "Not Found") let (statusCode, statusMessage) = http404Error print("The status code is \(statusCode)") print("The status message is \(statusMessage)") let (justTheStatusCode, _) = http404Error print("The status code is \(justTheStatusCode)") print("The status code is \(justTheStatusCode)") 16  Swift Language Intro - part 1 More on Tuples: We can name the elements when we declare the tuple let http404Error: (code: Int, message: String, fatal: Bool) = (404, "Not Found", false) print("The status code is \(http404Error.code)") print("The status message is \(http404Error.message)") if (http404Error.fatal) { print("Error is fatal") } else { print("Error is non-fatal") } We can also refer to the components numerically. let http404Error: (code: Int, message: String, fatal: Bool) = (404, "Not Found", false) print("The status code is \(http404Error.0)") print("The status message is \(http404Error.1)") print("The status fatal value is \(http404Error.2)") 17  Swift Language Intro - part 1 More on Tuples: Excellent for returning more than 1 value from a function. func getHttpError() -> (code: Int, message: String, isFatal:Bool) { return (404, "Not Found",true) } let z = getHttpError() print("Code is \(z.code). Message is \"\(z.message)\"") if z.isFatal { print("Fatal error occurred") } Can decompose them to access individual element values 18  Swift Language Intro - part 1 Tuples aren’t found in Objective C Have to decompose them if you’re passing them to Objective C methods (still some of these around in iOS). var s1 = "hello" var s2 = "world" (s1, s2) = (s2, s1) // now s1 is "world" and s2 is "hello" print(s1,s2) // prints “world hello" Assigning variable values directly to one another through a Tuple is safe. 19 Strings 20  Strings in Swift Unicode vs ASCII in C and Obj C, strings are arrays of ASCII characters (byte 0-255), represented in double quotes; i.e. "Hello ASCII folk!" Unicode character sets can represent alphabets of many more than 256 characters and each character may be represented by a multi-byte sequence. Objective C prefixes such a string with an “@“ to indicate it is Unicode: @"A Unicode string" In Swift, strings are composed of Unicode characters. No special stuff needed: "Hello from ! Unicode people!" let saved" = UserDefaults.standard.string(forKey: "phoneNumber") if let " = saved" { let promptText = "Your phone number is: " + " let numberInputText = " } 21  Strings in Swift Unicode vs ASCII in C and Obj C, strings are arrays of ASCII characters (byte 0-255), represented in double quotes; i.e. "Hello ASCII folk!" Unicode character sets can represent alphabets of many more than 256 characters and each character may be represented by a multi-byte sequence. Objective C prefixes such a string with an “@“ to indicate it is Unicode: @"A Unicode string" In Swift, strings are composed of Unicode characters. No special stuff needed: "Hello from ! Unicode people!" let 𝜋 = 3.1415926 let circumference = 2 * 𝜋 * radius let radius = 17.2 print("The circumference of a circle of radius \(radius) is \(circumference)”) // outputs The circumference of a circle of radius 17.2 is 108.07078544 22  Strings in Swift A String is a series of character values Each character is a single extended grapheme cluster (a sequence of 1 or more Unicode scalars) let myString = "# came to Earth in a $" A single character can be composed of multiple bytes - can’t index a string by Int (i.e. size of char representation * array index integer - not useful here ) e.g. this doesn’t work in Swift: print(myString) //this isn’t valid Swift - but can use a Range Strings are value types. (Copied when passed to a method or function 23  Strings in Swift Multiline strings!! let quotation = """ The White Rabbit put on his spectacles. "Where shall I begin, please your Majesty?" he asked. in Swift 4 "Begin at the beginning," the King said gravely, "and go on till you come to the end; then stop." """ The string starts on the first line following the opening quotes and ends on the last line before the closing quotes. Each new line is a new line in your string. To prevent this in a multiline string, use a\ let softWrappedQuotation = """ The White Rabbit put on his spectacles. "Where shall I begin, \ please your Majesty?" he asked. "Begin at the beginning," the King said gravely, "and go on \ till you come to the end; then stop." """ 24  Strings in Swift Raw strings!! in Swift 5.0 can specify a custom delimiter using the # symbol (alt-3) let myRawString = #"Did you say "Help me"?"# print(myRawString) //prints Did you say "Help me"? Characters in the string are treated literally. If you need to insert values from variables (or escape sequences), use additional # let user = "Phil" let myRawString = #"Did you say "Help me" \(user)?"# print(myRawString) //prints Did you say "Help me" \(user)? let user = "Phil" let myRawString2 = #"Did you say "Help me" \#(user)?"# print(myRawString2) //prints Did you say "Help me" Phil? 25  Strings in Swift Index a String using a String.Index (not Int), or a Range let myString = "An # came to Earth in a $" let firstIndex = myString.startIndex let firstCharacter = myString[firstIndex] print(firstCharacter) //prints A startIndex is the position of the first character in the string endIndex is the position after the last character in the string We can create an index to access a specific character, based on those indexes let index1 = myString.index(myString.startIndex, offsetBy: 3) let index2 = myString.index(myString.endIndex, offsetBy: -1) let aCharacter = myString[index1] let bCharacter = myString[index2] print(aCharacter, bCharacter) //prints ?? A: space and $ B: # and $ C: # and error 26  Strings in Swift Access individual characters of a String by iterating over the String itself. for character in "Dog!%"{ print(character) } // D // o // g // ! // % determine string length via.count let myString = "The weather looks like rain &" print(myString.count) //prints 29 27  Strings in Swift String concatenation and modification may not actually increase the string’s character count! var word = "cafe" print("the number of characters in \(word) is \(word.count)") // Prints "the number of characters in cafe is 4" word += "\u{301}" // COMBINING ACUTE ACCENT, U+0301 print("the number of characters in \(word) is \(word.count)") // Prints "the number of characters in café is 4” due to Swift’s use of extended grapheme clusters for Character values 28  Strings in Swift Unicode character encodings ~ ñ 0xF1 n 0x6E + 0x303 # Ruby one = “\u{F1}” ñ two = “\u{6E}\u{303}” ñ String concatenation and modification may not actually increase the string’s character count! 29  Strings in Swift Unicode character encodings ~ ñ 0xF1 n 0x6E + 0x303 # Ruby one = “\u{F1}” ñ two = “\u{6E}\u{303}” ñ one.length 1 two.length 2 one == two false String concatenation and modification may not actually increase the string’s character count! 30  Strings in Swift Unicode character encodings ~ ñ 0xF1 n 0x6E + 0x303 // swift let one = "\u{F1}" ñ let two = "\u{6E}\u{303}" ñ print(one.count) 1 print(two.count) 1 if one == two { print("The same!") The same! } String concatenation and modification may not actually increase the string’s character count! 31  Strings in Swift This is also evident in complex Emoji in Swift strings e.g.: ( = )+ * + ' joined to +++ joined to +)+ , let twoWomenHoldingHands = "\u{1f469}\u{1f3fc}\u{200d}\u{1f91d}\u{200d}\u{1f469}\u{1f3fd}" print(twoWomenHoldingHands,twoWomenHoldingHands.count) - ' 32  Strings in Swift ( = )+ * + ' joined to +++ joined to +.+ , let santa = "\u{1f385}" let womanHoldingHandsWithSanta = "\u{1f469}\u{1f3fc}\u{200d}\u{1f91d}\u{200d}\u{1f385}\u{1f3fd}" print(santa, "\n", womanHoldingHandsWithSanta, womanHoldingHandsWithSanta.count). /+0 33