How to capitalize the first letter in Swift

How to capitalize the first letter in each word

Swift string has the built-in string property, capitalized, that uppercase the first character in each word.

capitalized returns the new string with:

1. The first character in each word changed to its corresponding uppercase value.
2. All remaining characters set to their corresponding lowercase values.

Here is an example.

let hello = "hello, world!"
let shout = "UPPERCASED"
let lorem = "Itaque enim excepturi placeat aperiam sunt molestiae sint ea."

print(hello.capitalized)
// Hello, World!
print(shout.capitalized)
// Uppercased
print(lorem.capitalized)
// Itaque Enim Excepturi Placeat Aperiam Sunt Molestiae Sint Ea.

As you can see, capitalized property, capitalized every word. If you want to capitalize only the first letter of the first word in a sentence you have to do it yourself.

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How to capitalize the first letter in a sentence

There are many ways to do this, but I will show you one way.

I will create a new computed property for String called capitalizedSentence. And here is its behavior:

1. The first character in each sentence changed to its corresponding uppercase value.
2. All remaining characters set to their corresponding lowercase values.

extension String {
    var capitalizedSentence: String {
        // 1
        let firstLetter = self.prefix(1).capitalized
        // 2
        let remainingLetters = self.dropFirst().lowercased()
        // 3
        return firstLetter + remainingLetters
    }
}

1 First, we use the prefix(1) method to get the first letter of the string. Then, we capitalized it.
2 We remove the first letter using dropFirst() to get the remaining letters. Then, we lowercased them with lowercased().
3 Then, we combine the capitalized letter and the remaining lettters back together.

Here is an example of the same set of strings.

let hello = "hello, world!"
let shout = "UPPERCASED"
let lorem = "Itaque enim excepturi placeat aperiam sunt molestiae sint ea."

print(hello.capitalizedSentence)
// Hello, world!
print(shout.capitalizedSentence)
// Uppercased
print(lorem.capitalizedSentence)
// Itaque enim excepturi placeat aperiam sunt molestiae sint ea.

Caveat

The implementation I show you in this article is a basic one.

• It only works with a string that contains one sentence. The second sentence won't get capitalized.

let lorem = "doloremque nostrum. voluptas autem."
        
print(lorem.capitalizedSentence)
// Doloremque nostrum. voluptas autem.

• It doesn't work if the first string is a whitespace character and delimiter.

let hello = " hello"

print(hello.capitalizedSentence)
//  hello

I think you can take it from here and modify it to suit your need.