Learn SwiftUI (Day 3/100)

Swift

• Array
• Dictionary
• Set
• Enum

import Cocoa

// ## Arrays
var beatles = ["John", "Paul", "George"]
print(beatles)
beatles.append("Ringo")
print(beatles)
let numbers = [4, 8, 15, 16, 23, 42]
// numbers.append(43) // -> this is not allowed since numbers is constant
print(numbers)
// var temperatures = [25.3, 28.2, 26.4, "hello"]
// can't save both decimals and strings, an array can only have one type of data

// define an empty array
var names1 = Array<String>()
var names2 = [String]()
names2.append("John")
print(names2)
var names3: [String] = [] // use type hint
names3.append("Doe")
print(names3)


// array method
var numbers2 = [13,102,4,1,24]
print(numbers2.count)
let num = numbers2.remove(at: 0) // 13 will be removed, num is 13
print(num) // 13
print(numbers2)
print(numbers2.sorted()) // [1, 4, 24, 102], this will not change numbers2
print(numbers2.reversed()) // ReversedCollection, lazy operation
print(Array(numbers2.reversed())) // [24, 1, 4, 102]

// ## Dictionary
let employee2 = [
    "name": "Taylor Swift",
    "job": "Singer",
    "location": "Nashville"
]
print(employee2["name"]) // Optional("Taylor Swift"), the key may not exist
print(employee2["name"]!) // this will unwrap the optional to the actual value
print(employee2["height", default: "Unknown"]) // set the default value

// define an empty dictionary
var heights = [String: Int]()
heights["John"] = 6
print(heights)
var heights2: [String: Int] = [:]
heights2["John"] = 6
print(heights2)

// get count
print(heights2.count) // 1

// ## Set
var numbers4 = Set([1,2,3])
print(numbers4.count) // 3
numbers4.insert(3) // inserted: false
print(numbers4.count) // 3
print(numbers4.contains(2)) // true

// define an empty set
var numbers5 = Set<Int>()
numbers5.insert(1)
numbers5.insert(1)
numbers5.insert(5)
numbers5.insert(3)
print(numbers5.count) // 3
print(numbers5) // [5,3,1]
let numbers6 = numbers5.sorted()
print(numbers6) // numbers6 type is Array, not a Set, b/c set doesn't have order

// Enums
enum Weekday {
    case monday
    case tuesday
    case wednesday
    case thursday
    case friday
}

var day = Weekday.monday
day = .tuesday
day = .friday
print(day) // friday
/*
 Swift knows that .tuesday must refer to Weekday.tuesday 
 because day must always be some kind of Weekday.
 */