countConsonants()

Step 1: Understand the problem

The problem is to count the consonants in a given string. A consonant is any letter in the alphabet that is not a vowel(i.e., a, e, i, o, u). Therefore, all the remaining letters are consonants.

In Swift, Strings are collections of characters and each character is a separate entity that can be iterated over. Hence, we can solve this problem by iterating over the input string and checking if each character is a consonant.

let vowels = 'aeiou'
func isConsonant(char: Character) -> Bool {
    return !vowels.contains(char.lowercased())
}

Step 2: Create a counter

We need a counter to keep track of the number of consonants in a string. Initially, the counter is set to 0. Then for each character in the string, we check if it's a consonant, if so, we increment the counter.

var consonantCounter = 0

Step 3: Iterate through the string

We will use a for-in loop to go through each character in the string. For each character, we will use our isConsonant function to check if it's a consonant.

for char in str {
    if isConsonant(char: char) {
        consonantCounter += 1
    }
}

Step 4: Return the count

After we have gone through all of the characters in the string, our consonantCounter variable will hold the total number of consonants in the string. So, we return that value.

return consonantCounter

Conclusion

The full implementation of the function is as follows:

let vowels = 'aeiou'

func countConsonants(str: String) -> Int {
    var consonantCounter = 0
    
    func isConsonant(char: Character) -> Bool {
        return !vowels.contains(char.lowercased())
    }
    
    for char in str {
        if isConsonant(char: char) {
            consonantCounter += 1
        }
    }

    return consonantCounter
}

This function works by counting the number of consonants in a string. It first defines a helper function to determine whether a character is a consonant. It then initializes a counter to 0, iterates over the string, increments the counter for each consonant, and finally returns the counter.