How do I make vowels in a String uppercase in Swift?

I tried this:

func makeVowelsUpperCase(sentence:String)-> String {
    
    var result = String()
      
    var vowels = "aeiou"
    
    for i in vowels{
    
        if sentence.contains(i){
           result = sentence(i.uppercased())
        }
    }
    
  return result }

makeVowelsUpperCase(word: "this is my house")

CodePudding user response：

There's a few issues going on:

1. for i in vowels your for loop is iterating over the vowels. Within each loop body, you choose whether to keep your vowel or not depending on whether it's in the sentence or not.

   The result of this is that your result string could only ever be something like "AEIOU", "AIU", etc. (i.e., it will only be a string of length 0-5, only containing some subset of those vowels)

2. sentence(i.uppercased()) This part just doesn't make sense. sentence is a String, but by using parenthesis on it, it looks like you're tryign to call it, as if it were a function (but it's not). Hence the error: "error: incorrect argument label in call (have 'word:', expected 'sentence:')"

3. You're reassigning result in the loop body, which means your result could only ever contain one character. Instead, you should make one intermediate value once, and append onto it from there.

4. The way you're trying to call makeVowelsUpperCase (with an argument label of word:) doesn't match the way it's declared (with an argument label of sentence:).

I think this is what you had in mind:

func makeVowelsUpperCase(sentence: String) -> String {
    var result = String()
    let vowels = "aeiou"
    
    for char in sentence {
        if vowels.contains(char) {
            result.append(char.uppercased())
        } else {
            result.append(char)
        }
    }
    
    return result
}

makeVowelsUpperCase(sentence: "this is my house")

There's a few other issues I'd point out:

1. vowels is declared mutable (var instead of let). Why would the set of vowels be mutable? They should always just be "aeiou" (for English, at least).

2. The loop variable is called i, which is conventional for a loop variable that's an index of some array, but in this case, it's a Character.

3. The keyword label, sentence is a little misleading. There's no real requirement that the input be a sentence. It could be a word, or a paragraph, and everything would still work as normal.

4. This for loops is just implementing a mapping operation, where an input sequence (the characters of the input) is mapped into the output sequence (the potentially uppercased characters of the output) using some transformation (uppercase if vowel). This is precisely what Array.map is for.

   There's just one catch here. As it turns out, in some languages, the uppercased version of one character might actually be multiple characters. To account for this, Character.uppercased() doesn't actually return a Character, it returns a String.

   To cope with this, we need to use flatMap instead of map, which will have the effect of joining these strings returned as a result of each character-upper-casing operation.

Here's how I might right this:

func uppercaseVowels(_ input: String) -> String {
    let vowels = "aeiou"
    
    let newChars = input.flatMap { char in
        vowels.contains(char) ? char.uppercased() : String(char)
    }
    
    return String(newChars)
}

print(uppercaseVowels("this is my house"))

CodePudding user response：

You can try

func makeVowelsUpperCase(_ sentence:String)-> String {
    var result = sentence
    let vowels = "aeiou"
    vowels.forEach {
        result = result.replacingOccurrences(of: "\($0)", with: "\($0)".uppercased())
    }
    return result 
}

Call

let str = makeVowelsUpperCase("this is my house")  
print(str) // thIs Is my hOUsE

CodePudding user response：

You can do it with simple code like below :

var word : String = "this is my house "
var vowels = "aeiou"

let result = word.map { vowels.contains($0) ? String($0).uppercased() : String($0) }
            .joined()
print(result)

OUTPUT :

thIs Is my hOUsE 

In a function :

func uppercaseVowels(_ input: String) -> String {

    let result = input.map { vowels.contains($0) ? String($0).uppercased() : String($0) }
                .joined()

    return result
}

print(uppercaseVowels(word))