CODEWITHSUNDEEP
swiftswift3
lmiguelvargasf
lmiguelvargasf

Reputation: 69745

Cannot use mutating member on immutable value inside a closure

I try to capitalize the first letter of each word of a string, and I have the following code:

func makeHeadline(string: String) -> String {
        let headline = words.map { (word) -> String in
        var word = word
        let firstCharacter = word.remove(at: word.startIndex)
        return "\(String(firstCharacter).uppercased())\(word)"
        }.joined(separator: " ")

        return headline
    }

However, I get the following error:

Cannot use mutating member on immutable value: 'word' is a 'let' constant.

I tried adding var before word (var word), but I get the error:

Parameters may not have the 'var' specifier.

How can I solve this?

Upvotes: 1

Views: 5863

Answers (1)

Alexander
Alexander

Reputation: 63167

Make a local mutable copy:

func makeHeadline(string: String) -> String {
    let words = string.components(separatedBy: " ")

    let headline = words.map { (word) -> String in
        var word = word
        let firstCharacter = word.removeAtIndex(word.startIndex)
        return String(firstCharacter).uppercaseString + word
    }.joined(separator: " ")

    return headline
}

Upvotes: 7

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