斯威夫特3.0

“Hello World”

nameOfString.capitalized

或“HELLO WORLD”

nameOfString.uppercased

编辑:这不再适用于文本，现在只支持输入字段。

以防有人以同样的问题结束这里关于SwiftUI:

// Mystring is here
TextField("mystring is here")
   .autocapitalization(.sentences)


// Mystring Is Here
Text("mystring is here")
   .autocapitalization(.words)

Swift 2.0(单行):

String(nameOfString.characters.prefix(1)).uppercaseString + String(nameOfString.characters.dropFirst())

斯威夫特4.0

string.capitalized(with: nil)

or

string.capitalized

但是，每个单词的首字母都要大写

苹果公司的文档:

A capitalized string is a string with the first character in each word changed to its corresponding uppercase value, and all remaining characters set to their corresponding lowercase values. A “word” is any sequence of characters delimited by spaces, tabs, or line terminators. Some common word delimiting punctuation isn’t considered, so this property may not generally produce the desired results for multiword strings. See the getLineStart(_:end:contentsEnd:for:) method for additional information.

如果你的字符串都是大写，那么下面的方法将工作

labelTitle.text = remarks?.lowercased().firstUppercased

这个扩展将帮助你

extension StringProtocol {
    var firstUppercased: String {
        guard let first = first else { return "" }
        return String(first).uppercased() + dropFirst()
    }
}

func helperCapitalizeFirstLetter(stringToBeCapd:String)->String{
    let capString = stringToBeCapd.substringFromIndex(stringToBeCapd.startIndex).capitalizedString
    return capString
}

也工作，只是传递你的字符串，并得到一个大写的回来。