Swift .uppercaseString or .lowercaseString property replacement

Question

Since Strings in Swift no longer have the .uppercaseString or .lowercaseString properties available, how would i go about performing that function?

If i have for example

Answer 1

Swift 4 & 5

TL;DR

The new names in Swift 3 use the -ed postfix to indicate that uppercased() and lowercased() return a copy rather than a modified original:

import Foundation

let title = "Castration: The Advantages and the Disadvantages" // Don't `var` unless you have to!
title.uppercased() // "CASTRATION: THE ADVANTAGES AND THE DISADVANTAGES"
title.lowercased() // "castration: the advantages and the disadvantages"
title.capitalized  // "Castration: The Advantages And The Disadvantages"

Inconsistencies: .method() vs .property

Note the odd discrepancy where uppercased() and lowercased() are functions, while capitalized is a property. This seems like an oversight, in which case hopefully someone comfortable with the swift evolution process will make a correction before 3.0 leaves beta.

If happen to know you're working with NSString, there is a property available for all three:

NSString(string: "abcd").uppercased
NSString(string: "ABCD").lowercased
NSString(string: "abCd").capitalized

Language is Hard

The methods above hide a whole string of method delegations to NSString and CFString with a default Locale of nil. This works most of the time. At least, it does in English. The fact is, I don't really understand the rest of what I'm about to paste from my playground.

let turkishI = "\u{0130} is not I"                  // "İ is not I"
turkishI.uppercased()                               // "İ IS NOT I"
turkishI.uppercased(with: Locale(identifier: "en")) // "İ IS NOT I"
turkishI.uppercased(with: Locale(identifier: "tr")) // "İ İS NOT I"
turkishI.lowercased()                               // "i̇ is not i"
turkishI.capitalized                                // "İ Is Not I"
turkishI.lowercased(with: Locale(identifier: "en")) // "i̇ is not i"
turkishI.lowercased(with: Locale(identifier: "tr")) // "i is not ı"

Swift 3

The Locale initializer has a slightly longer parameter name in Swift 3…

turkishI.uppercased(with: Locale(localeIdentifier: "en"))

Light Humor

"✈️".uppercased()  //