Swift flatmap, map, filter, reduce prractice

Practice.swift

//: Playground - noun: a place where people can play

import UIKit

// Map
let fruits0 = ["apple", "banana", "orange", ""]
let counts0 = fruits0.map { fruit0 -> Int? in
    let length = fruit0.characters.count
    guard length > 0 else {
        return nil
    }
    return length
}
// [Optional(5), Optional(6), Optional(6), nil]
print(counts0)


// FlatMap use
let fruits = ["apple", "banana", "orange", ""]
let counts = fruits.flatMap { fruit -> Int? in
    let length = fruit.characters.count
    guard length > 0 else {
        return nil
    }
    return length
}

// [5,6,6]
print(counts)

let array = [[1,2,3], [4,5,6], [7,8,9]]
// Map
let arrayMap = array.map { $0 }
// [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
print(arrayMap)
// flatMap
let arrayFlatMap = array.flatMap { $0 }
// [1, 2, 3, 4, 5, 6, 7, 8, 9]
print(arrayFlatMap)


// Filter
let numbers = [1,2,3,4,5,6]
let evens = numbers.filter { $0 % 2 == 0 }
// [2, 4, 6]
print(evens)


// Reduce
let numbers1 = [1,2,3,4,5]
// reduce first parameter is initial value
let sum = numbers1.reduce(0) { $0 + $1 }
let sum1 = numbers1.reduce(0) { total, num in
    return total + num
}
// 15
print(sum)