Swift Basics - from Pirple.com

Swift Basics - from Pirple.com

Variable declaration

    // 1

    var/let name : type = value
    
    // 2

    var/let name : type
    name = value

    // 3

    var/let name = value
Primitive types

Int, Int8, Int16, Int32, Int64, UInt, UInt8, UInt16, UInt32, UInt64
Float(32), Double(64), CGFloat(Similar to Float)
Bool
Character

    // Valid. length=1

    var char1 : Character = "?" 
     
    // Invalid, length=0  

    var char2 : Character = ""

Emojis can be represented with Character

Strings

Not a primitive type 

    let name : String = "Mammoth Interative"
    let startIndex = name.index(name.startIndex, offsetBy: 3)
    let endIndex = name.index(name.startIndex, offsetBy: 7)
    let moth : String = name.substring(with: startIndex..<endIndex)  
    // Result: moth

Multilevel string: 

    let multilineString : String = """
        Hello how are you?
        I'm doing well, how are you?
    """

Optional: 

    let test : String? = "Axe"
    test = nil

Tuples

Tuples are variables/constants with multiple values 

    // syntax

    var/let name : (val_type1, val_type2) = (val1, val2)
    
    let item : (String,Int) = ("Food", 10)
    let itemName : String = item.0
    let itemQuantity : Int = item.1
    
    // another way

    let (name, quantity) = item
    let (name, _) = item
    
    // assigning param name 

    let item2 = (name: "Matches", qty: 15)

Type Convertion

Double(10)
Float(15)
Int(50.79) // 50
String(50) // "50"

Conditional Operators

==, !=, <, ⇐, >, >=, ===, !==

Logical

&&, ||, |

Ternary

a ? result_if_true : result_if_false

Nil-coalescing

a ?? b int1 = int2 ?? 10 // if int2 is nil, then int1 will be assigned to 10

Collections

Collection types

Arrays

    var inventory : [String] = ["food", "hat", "coat"]
    
    // reassigning

    inventory = ["food", "shirt"]

    //multiple type values

    var randomArray : [Any] = [1, false, "hello"]

    // type of declarations

    var array1 : [Int] = []
    var array2 = [Int]()

    // assigning value

    var array3 : [Int] = [0,0,0,0,0,0]
    // defaulting value in array

    var array4 : [Int] = Array(repeating: 0, count: 5)

Retrieve Elements/Attributes :

    var inventory : [(String,Int)] = [("Gloves",2),("Fruit",4),("Axe",1)]
    let secondItem : (String, Int) = inventory[1]

    //handling of nil and access to first element

    let firstItem : (String,Int)? = inventory.first
    // getting the inner value

    let thirdItemName : String = inventory[2].0

    //to find item in array

    let array2 : [Int] = [1,4,2,5,7]
    array2.contains(10)

Modify Array/Elements :

    // modify array

    inventory = [("Gloves",3),("Fruit",5),("Shoes",6)]
    // modify item

    inventory[1] = ("Gloves", 2)

    // update second and third items in array

    inventory[1...2] = [("fish",3), ("socks", 9)]

    // append item

    inventory.append(("Glasses", 1))
    // or

    inventory += [("fish",3), ("socks", 9)]

    // insert at position

    inventory.insert(("Hat",2), at: 2)

    // remove item

    inventory.remove(at: 0)

Multi-dimentional Array

    // multi-dim array

    var shoppingList : [[String]] = [
        ["fruit","cheese","bread"],
        ["t-shirt","shorts"],
        ["paper towel"]]

    // retrieve data

    let shorts : String = shoppingList[1][1]
    let bread : String = shoppingList[0][2]

Ranges

    // range as var

    var range1 = 1...10
    var range2 = 1..<10
    let higherThan5 = 6...

    for number in range1 {
        print(number)
    }

    // use of range with array

    let numArray : [Int] = [1,2,4,5,7,8,9]
    for number in numArray[4...] {
        print(number)
    }

Range can be used in Switch statement as well. 

    var health : Int = 95

    switch health {
    case 100:
        print("full health")
    case 50..<100:
        print("healthy")
    case 1..<50:
        print("low health")
    case 0:
        print("dead")
    default :
        print("health out of range")
    }

Checking nil value: 

    var item : String? = "Fruit"
    var itemName : String = ""

    // checking nil

    if (item != nil) {
        itemName = item! //unwrapping

    }

    // another way

    if let itemName = item {
        // execute code based on itemName

    }

    // another different approach is

    func doSomething() {
        guard let itemName3 = item else { return }
        print(itemName3)
    }
    doSomething()

Disctionaries