Reverse every even or every odd word in string in swift

Following task - reverse every even or every odd word in sentence.

Algorithm

1. Get array of words from string (sentence)
2. Create new empty string
3. In for loop go through the array and according to condition reverse word or not and append it to new string

Let's get implemented our algorithm.

import UIKit

let str = "This is the string which will be reverted particaually"

enum WhichNumer: Int {
    case Even = 0
    case Odd = 1
}

func reverseWords(str: String, number: WhichNumer = .Even) -> String {
    let array = str.components(separatedBy: " ")
    var newStr = ""
    for i in 0..<array.count {
        if newStr != "" {
            newStr += " "
        }
        let word = array[i]
        if (i + 1) % 2 == number.rawValue {
            newStr += String(word.reversed())
        } else {
            newStr += word
        }
    }
    
    return newStr
}

print(reverseWords(str: str))
// This si the gnirts which lliw be detrever particaually

print(reverseWords(str: str, number: .Odd))
//sihT is eht string hcihw will eb reverted yllauacitrap

But we can improve our code with using High-ordered function. 

There is following algorithm:

1. Create array of string from initial string

str.components(separatedBy: " ")
// ["This", "is", "the", "string", "which", "will", "be", "reverted", "particaually"]

2. Convert this array to enumerated. According to Apple Documentation after this we can get sequence of pairs with index and value.

"Returns a sequence of pairs (n, x), where n represents a consecutive integer starting at zero, and x represents an element of the sequence."

str.components(separatedBy: " ").enumerated()
//    0 : This
//    1 : is
//    2 : the
//    3 : string
//    4 : which
//    5 : will
//    6 : be
//    7 : reverted
//    8 : particaually

3. Now we can use map function to this array of pairs. We check index and modify value if needed.

str.components(separatedBy: " ").enumerated().map { (index, value) -> String in
    if ((index + 1) % 2 == number.rawValue) {
        return String(value.reversed())
    }
    return value
})
// ["This", "si", "the", "gnirts", "which", "lliw", "be", "detrever", "particaually"]

4. Finally, array of words can be convert to string with joined function.

let newStr = str.components(separatedBy: " ").enumerated().map { (index, value) -> String in
    if ((index + 1) % 2 == number.rawValue) {
        return String(value.reversed())
    }
    return value
}.joined(separator: " ")
// This si the gnirts which lliw be detrever particaually

Here new implementation of our function.

func reverseWordsUsingHOF(str: String, number: WhichNumer = .Even) -> String {
    let newStr = str.components(separatedBy: " ").enumerated().map { (index, value) -> String in
        print(index)
        if ((index + 1) % 2 == number.rawValue) {
            return String(value.reversed())
        }
        return value
    }.joined(separator: " ")
    
    return newStr
}

print(reverseWordsUsingHOF(str: str))
// This si the gnirts which lliw be detrever particaually