extension String {
    func makeHTMLfriendly() -> String {
        var finalString = ""
        for char in self {
            for scalar in String(char).unicodeScalars {
                finalString.append("&#\(scalar.value)")
            }
        }
        return finalString
    }
}

用法:

newString = oldString.makeHTMLfriendly()

这似乎可以正常使用(尽管我不确定Unicode标量始终与HTML数字匹配).

This appears to work in general (although I don't know for sure that unicode scalars always match HTML numbers).

请注意，它会转换所有内容，甚至包括不需要真正转换的字母数字字符.编辑它以不进行某些转换可能并不难.

Note that it converts everything, even things like alphanumeric characters that don't really need to be converted. It probably wouldn't be too difficult to edit it to not convert some things.