```swift
import Cocoa

/* Create a simple closure */
let sayHello = {
    print("Hello, World!")
}

/* Call the closure */
sayHello()

/* Create a function that can take a closure as a parameter */
func sayHelloTo(name: String, withGreeting greeting: () -> ()) {
    print("Hello, \(name)!")
    greeting()
}

/* Call the function, passing in the closure */
sayHelloTo(name: "John", withGreeting: sayHello)
```

### Output
Hello, World!

Hello, John!

Hello, World!


Swift: Pass a closure to function

```swift
import Cocoa

/* Create a array of months from Jan to Jun */
var months = ["Jan", "Feb", "Mar", "Apr", "May", "Jun"]
print(months)

/* Create a function to swap random elements in the array */
func swapRandomElements(array: inout [String]) {
    let firstIndex = Int(arc4random_uniform(UInt32(array.count)))
    let secondIndex = Int(arc4random_uniform(UInt32(array.count)))
    let temp = array[firstIndex]
    array[firstIndex] = array[secondIndex]
    array[secondIndex] = temp
}

/* swap the months */
swapRandomElements(array: &months)
print(months)

/* swap the months 2 times */
swapRandomElements(array: &months)
swapRandomElements(array: &months)
print(months)

/* swap the months 10 times */
for _ in 1...10 {
    swapRandomElements(array: &months)
}
print(months)
```
### Output
["Jan", "Feb", "Mar", "Apr", "May", "Jun"]

["Jan", "Apr", "Mar", "Feb", "May", "Jun"]

["Jan", "Mar", "Jun", "Feb", "May", "Apr"]

["May", "Apr", "Jun", "Feb", "Mar", "Jan"]

Swift: swap random elements in an array

```swift
import Cocoa

/* Create a uuid */
let uuid = UUID().uuidString
print(uuid)

/* remove dashes from uuid */
let uuidWithoutDashes = uuid.replacingOccurrences(of: "-", with: "")

print(uuidWithoutDashes)

/* remove all characters from the uuid */
let uuidWithoutAllCharacters = uuidWithoutDashes.replacingOccurrences(of: "[A-Z]", with: "", options: .regularExpression)

print(uuidWithoutAllCharacters)

/* get the last character from the uuid */
let lastCharacter = uuidWithoutAllCharacters.last
print(lastCharacter!)

/* check if the last character is a even or odd number */
let isEven = Int(String(lastCharacter!))! % 2 == 0
print(isEven)
```

### Output
985BCADD-D907-4D19-B48A-22A1D8067704

985BCADDD9074D19B48A22A1D8067704

985907419482218067704

4

Swift: UUID to odd or even number

```swift
import Cocoa

/* Create an array of 5 intergers with duplicate values */
let array = [1, 2, 3, 4, 5, 1, 2, 3, 4, 5]
print(array)

/* remove duplicate values from the array */
let set = Set(array)
print(set)
```

### Output

[1, 2, 3, 4, 5, 1, 2, 3, 4, 5]

[4, 1, 5, 2, 3]

Swift: remove duplicates from array

```swift
import Cocoa

/* Create an array of 2 negative integers */
var negativeIntegers = [-1, -2]

/* print the array */
print(negativeIntegers)

/* Create an array of 2 positive integers */
var positiveIntegers = [1, 2]

/* print the array */
print(positiveIntegers)

/* Merge the two arrays */
var allIntegers = negativeIntegers + positiveIntegers

/* print the array */
print(allIntegers)
```

### Output
[-1, -2]

[1, 2]

[-1, -2, 1, 2]

Swift: Merging of 2 integer arrays

```swift
import Cocoa

/* Create an array of 5 integers */
var myArray = [1, 2, 3, 4, 5]

/* print the array */
print(myArray)

/* using closure, add 1 to each element of the array */
myArray = myArray.map({$0 + 1})

/* print the array */
print(myArray)
```

### Output
[1, 2, 3, 4, 5]

[2, 3, 4, 5, 6]

Swift: Add 1 to each element of an integer array

```swift
import Cocoa

/* Swift: Add 2 numbers using function */
func addNumbers(num1: Int, num2: Int) -> Int {
    return num1 + num2
}

print(addNumbers(num1: 1, num2: 2))

/* Swift: Add 2 numbers using closure */

let addNumbersClosure = { (num1: Int, num2: Int) -> Int in
    return num1 + num2
}

print(addNumbersClosure(1, 2))
```

### Output
3

3

Swift: Add 2 numbers using function or closure

```swift
import Cocoa

/* Create a function that takes a string and returns a string. */
func sayHello(name: String) -> String {
    return "Hello \(name)!"
}
/* print the result of calling sayHello with "Cocoa" as the argument. */
print(sayHello(name: "Cocoa"))

/* Create a closure that takes a string and returns a string. */
let sayHelloClosure = { (name: String) -> String in
    return "Hello \(name)!"
}
/* print the result of calling sayHelloClosure with "Cocoa" as the argument. */
print(sayHelloClosure("Closure"))
```

### Output
Hello Cocoa!

Hello Closure!

Swift: Function vs Closure

```swift
import Cocoa

/* Create an array of 5 integers */

var myArray = [1, 2, 3, 4, 5]

/* Using reduce, sum the values in the array */

var sum = myArray.reduce(0, +)

/* Print the sum */
print(sum)
```

### Output
15

Swift:  Sum an array of integers using reduce

```swift
import Cocoa

/* How many friday the 13th in the year 2023? */
let year = 2023
let calendar = Calendar.current
let dateComponents = DateComponents(year: year, month: 1, day: 1)
let date = calendar.date(from: dateComponents)!
let range = calendar.range(of: .month, in: .year, for: date)!
let months = range.count
var friday13th = 0
for month in 1...months {
    let dateComponents = DateComponents(year: year, month: month, day: 13)
    let date = calendar.date(from: dateComponents)!
    let weekday = calendar.component(.weekday, from: date)
    if weekday == 6 {
        friday13th += 1
    }
}
print(friday13th)
```

## Output
2

Swift: How many friday the 13th in the year 2023?

```swift
import Cocoa

/* How many days are there in the month of December 2023? */

let calendar = Calendar.current
let dateComponents = DateComponents(calendar: calendar, year: 2023, month: 12)
let date = calendar.date(from: dateComponents)!
let range = calendar.range(of: .day, in: .month, for: date)!
let days = range.count

print("There are \(days) days in December 2023")
```

## Output
There are 31 days in December 2023

Swift: How many days are there in the month of December 2023?

```swift
import Cocoa

/*  Create a random list of 5 even numbers between 0 and 100.  */

var evenNumbers = [Int]()
for _ in 1...5 {
    var randomNumber = Int(arc4random_uniform(50))
    randomNumber *= 2
    evenNumbers.append(randomNumber)
}

print(evenNumbers)
```

### Output
[72, 82, 64, 84, 52]

Swift:  Create a random list of 5 even numbers between 0 and 100

```swift
import Cocoa

/* Create a 3 letter list of the first 6 months of the year */
let months = ["Jan", "Feb", "Mar", "Apr", "May", "Jun"]

/* de-capitalize the list of months */
let lowerMonths = months.map { 
    $0.lowercased()
}

/* print the list of months */
print(lowerMonths)

/* Capitalize the first letter of the list of months */
let capitalizedMonths = months.map { 
    $0.capitalized
}

/* print the list of months */
print(capitalizedMonths)
```

## Output
["jan", "feb", "mar", "apr", "may", "jun"]

["Jan", "Feb", "Mar", "Apr", "May", "Jun"]

Swift: Capitalize and de-capitalize a list

```swift
import Cocoa

//Is 2023 a leap year?
let isLeapYear = 
2023 % 4 == 0 && (2023 % 100 != 0 || 2023 % 400 == 0)

if isLeapYear {
    print("2023 is a leap year")
} else {
    print("2023 is not a leap year")
}
```

## Output
2023 is not a leap year

<iframe width="560" height="315" src="https://www.youtube.com/embed/IcXHEJfmVLA" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

Swift: Is 2023 a leap year?

```swift
import Cocoa

//Swift define a string
let str = "A Quick Brown Fox Jumps Over The Lazy Dog"

//print the string
print(str)

//reverse the string word by word
let reversed = 
str.components(separatedBy: " ").reversed().joined(separator: " ")

//print the reversed string
print(reversed)
```

### Output
A Quick Brown Fox Jumps Over The Lazy Dog

Dog Lazy The Over Jumps Fox Brown Quick A

<iframe width="560" height="315" src="https://www.youtube.com/embed/yovSbEuZAU0" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>


Swift: Reverse a string word by word

```kotlin
fun main() {

    //define a list of 3-letter months from Jan to Jun
    val months = listOf("Jan", "Feb", "Mar", "Apr", "May", "Jun")
    //put "May" as the first element of the list
    val months2 = months.toMutableList()
    months2.add(0, months2.removeAt(4))

    println(months2)

}
```

### Output
[May, Jan, Feb, Mar, Apr, Jun]

Put element as the first in the list

```kotlin
import java.time.LocalDate
import java.time.format.DateTimeFormatter
import java.util.*

fun main() {

    //convert string 2022-08-31T09:05:05.000Z to date
    val date = "2022-08-31T09:05:05.000Z"
    val formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'")
    val localDate = LocalDate.parse(date, formatter)
    println(localDate)

    //convert localDate to the format "MMM dd, yyyy"
    val formatter2 = DateTimeFormatter.ofPattern("MMM dd yyyy")
    val formattedDate = localDate.format(formatter2)
    println(formattedDate)

}
```

### Output
2022-08-31
Aug 31 2022