Swift 5 - Strings

What is a String?

• Hey, did you know a string in swift is a struct under the hood?
• This means that strings are passed by value and have several properties and methods that we can use to manipulate our strings
• To instantiate a string, use parentheses, like let myCoolString = String()

Mutating

• Many of the functions for string manipulation are mutating - they modify the string variable’s contents directly, instead of returning a new string.
• You’ll see that each of the below functions have a mutating keyword before it’s function declaration.
• Examples:
  • append()
    • mutating func append(_ other: String)
  • removeFirst()
    • @discardableResult mutating func removeFirst() -> Character
  • removeLast()
    • @discardableResult mutating func removeLast() -> Character

Swift 5 - Collections

What is an Array?

• An array is list of ordered items

var numbers = Array<Double>()

//: This is syntactic sugar for the above
var moreNumbers = [Double]()

//: Array literal syntax. Uses type inference to determine the type is an array of doubles
let differentNumbers = [97.5, 98.5, 99.0]

What is a Dictionary?

• An dictionary is a list of unique key,value pairs

var myDictionary = [String:String]()

//: This is syntactic sugar for the above
var addressBook = ["jess": "123 Drury Lane", "bob": "345 Candy Lane", "alice": "85 Yellow Brick Road"]

Removing Items from Dictionary

var presidentialPetsDict = ["Barack Obama":"Bo", "Bill Clinton":"Socks",
    "George Bush":"Miss Beazley", "Ronald Reagan":"Lucky"]

presidentialPetsDict["George W. Bush"] = presidentialPetsDict["George Bush"] 
presidentialPetsDict["George Bush"] = nil 

//: Same as above
var oldValue = presidentialPetsDict.removeValueForKey("George Bush")
presidentialPetsDict["George W. Bush"] = oldValue

What is an Set?

• An set is a list of unique, unordered items

var students = Set<String>()

//: This is syntactic sugar for the above
var students:Set = ["student1", "student2", "student4"]

No Duplicates Allowed!

• You can try to add duplicates to the set, but Swift will not update the Set with the duplicate because sets have no duplicates

var students:Set = ["student1", "student2", "student4"]
// This does nothing
student.insert("student1")