String(localized: "YOUR_LOCALIZED_KEY") 

NSLocalizedString("Abenteuer", comment: "")
String(format: NSLocalizedString("%d Units in: %@", comment: ""), inventoryItem.amount, inventoryItem.place.title)

String.localizedStringWithFormat(NSLocalizedString("%d unit(s) in: %@", comment: "Message for stock in place"), self.amount, self.place.title)

1. Neue plist erzeugen und in "Localizable.stringsdict" umbenennen
2. Vorlage verwenden
3. Stringsdict localisieren

<plist version="1.0">
    <dict>
        <key>%d file(s) remaining</key>
        <dict>
            <key>NSStringLocalizedFormatKey</key>
            <string>%#@files@</string>
            <key>files</key>
            <dict>
                <key>NSStringFormatSpecTypeKey</key>
                <string>NSStringPluralRuleType</string>
                <key>NSStringFormatValueTypeKey</key>
                <string>d</string>
                <key>one</key>
                <string>%d file remaining</string>
                <key>other</key>
                <string>%d files remaining</string>
            </dict>
        </dict>
    </dict>
</plist>