How to get localized Cancel, Done and etc?

Encouraged by Answer to this Question (by Stephan Heilner) and Answer (by bdunagan) for iPhone/iOS: How can I get a list of localized strings in all the languages my app is localized in?

Objective-C

NSString * LocalizedString(NSString *key) {
    return [[NSBundle mainBundle] localizedStringForKey:key];
}

@interface NSBundle(Localization)
- (NSString *)localizedStringForKey:(NSString *)key;
- (NSDictionary<NSString *, NSString *> *)localizationTable;
@end

@implementation NSBundle(Localization)
- (NSDictionary<NSString *, NSString *> *)localizationTable {
    NSString *path = [self pathForResource:@"Localizable" ofType:@"strings"];
    NSData *data = [NSData dataWithContentsOfFile:path];
    NSError *error = nil;
    id obj = [NSPropertyListSerialization propertyListWithData:data options:NSPropertyListImmutable format:NULL error:&error];
    if (error && obj == nil) {
        @throw error;
        return nil;
    }
    if ([obj isKindOfClass:NSDictionary.class]) {
        return obj;
    }    
    @throw NSInternalInconsistencyException;
    return nil;
}

- (NSString *)localizedStringForKey:(NSString *)key {
    return [self localizedStringForKey:key value:nil table:nil];
}
@end

Swift 5

public extension String {
    func localized(_ bundle: Bundle = .main) -> String {
        bundle.localize(self)
    }        
    var localized: String {
        return localized()
    }
}

extension Bundle {
    static var UIKit: Bundle {
        Self(for: UIApplication.self)
    }
    func localize(_ key: String, table: String? = nil) -> String {
        self.localizedString(forKey: key, value: nil, table: nil)
    }
    var localizableStrings: [String: String]? {
        guard let fileURL = url(forResource: "Localizable", withExtension: "strings") else {
            return nil
        }
        do {
            let data = try Data(contentsOf: fileURL)
            let plist = try PropertyListSerialization.propertyList(from: data, format: .none)
            return plist as? [String: String]
        } catch {
            print(error)
        }
        return nil
    }
}

Usage:

"Photo Library".localized(.UIKit)

To get all keys of localized strings of UIKit:

Bundle.UIKit.localizableStrings?.keys//.map { $0 }

One (admittedly questionable) way of accomplishing this easily is use Apple's framework bundle localizations directly:

To see what they have to offer, open the following directory via the Finder:

/Applications/Xcode/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator6.1.sdk/System/Library/Frameworks

And in your case, you'll subsequently open ./UIKit.framework/English.lproj/Localizable.strings (in TextMate). Here you see a wide variety of translations that Apple uses for things like "Print", "OK", "On", "Off", etc. The real magic is that there are about 35 different language translations that you can copy into your own Localizable.strings files, for free.

If you are incredibly brazen and don't mind putting your app's future stability in question, you could skip the whole "copy into your own Localizable.strings" process and go straight to the source programmatically:

NSBundle *uiKitBundle = [NSBundle bundleWithIdentifier:@"com.apple.UIKit"];
NSString *onText = uiKitBundle ? [uiKitBundle localizedStringForKey:@"Yes" value:nil table:nil] : @"YES";
NSString *offText = uiKitBundle ? [uiKitBundle localizedStringForKey:@"No" value:nil table:nil] : @"NO";

---

Caveat: In no way do I recommend that you actually access these localized resources programmatically in an app that you intend to submit to the App Store. I'm merely illustrating a particular implementation that I've seen which addresses your original question.

Here's a little macro I created to get the System UIKit Strings:

#define UIKitLocalizedString(key) [[NSBundle bundleWithIdentifier:@"com.apple.UIKit"] localizedStringForKey:key value:@"" table:nil]

Use it like this:

UIKitLocalizedString(@"Search");
UIKitLocalizedString(@"Done");
UIKitLocalizedString(@"Cancel");
...