Collections in Swift

collections_in_swift

// Collections in Swift

// Two basic collection types in Swift, Arrays and Dictionaries.

// Arrays in Swift

// Ordered collections of items
// Zero based.
// Type safe
// If defined by let, it is immutable, can not be added or altered.
// If dfined by var, it is mutable, can be modifed and added.

var a1 = [2, 3, 4]
var a2 : [Int]
a1[2] = 8
a1.append(5)
a1 += [6]
a1.insert(1, atIndex: 0)
a1.removeLast() // removes the last item from array and returns the removed item.
a1.count

for i in a1 {
    println(i)
}


// Dictionaries in Swift

// A dictionary is a collection of Key value pairs.
// keys are strrictly typed.
// Values are strictly typed.

var d1 = [1: "One", 2: "Two", 3: "Three"]
var d2 : [Int: String]
d1[4] = "Four"
d1[0] // returns nil
d1[1] //returns "ONe
d1.updateValue("FOUR", forKey: 4)
d1.removeValueForKey(4)
d1.count

for (k, v) in d1{
    println("\(k) corresponds to \(v)")
}


// Tuples in Swift

// Tuples are a clollection of any items
var t1 = ("Ruby", 3, true)

// A function can return a tuple
func someFunction() -> (Int, String){
    return (2, "Some string")
}

someFunction()
let r1 = someFunction()
r1.0 // returns 2
r1.1 // returns "Some String"

let (r2, r3) = someFunction()
r2 // returns 2
r3 // returns "Some String"


// Optionals in Swift

// The data which is missing and data which is zero(or default) or data which is nil are different.

var temperature :Int? // means that this variable can be an integer or nil

println("Temperature is: \(temperature)") //  returns"Temperature is: nil"

temperature = 37

if temperature != nil{
    println("Temperature is: \(temperature)") // returns "Temperature is: Optional(37)"
    println("Temperature is: \(temperature!)") // returns ""Temperature is: 37""
}


// Enumerators in Swift

enum SteakPreference {
    case wellDone
    case medium
    case rare
    case blueRare
}

var mySteakPreference = SteakPreference.medium
var JackSteakPreference : SteakPreference
JackSteakPreference = .wellDone



// Closures in Swift

// A self-cntained, reusable group of code
// A function is a type of closure.

let c1 = {
    println("Hello World!")
}

func f1 (c : ()->()){
    for i in 1...5 {
        c()
    }
}

f1(c1)

func f2 ()->(){
    println("Hello World!")
}

// Turning aboce function into a closure:

var c2 = {
    ()->() in
    println("Hello World!")
}

f1({()->() in println("Hello World!")})