Swift 3解决方案:

let languages = ["bs", "zh-Hant", "en", "fi", "ko", "lv", "ms", "pl", "pt-BR", "ru", "sr-Latn", "sk", "es", "tr"]
UserDefaults.standard.set([languages[0]], forKey: "AppleLanguages")

给出了一些可以使用的语言代码的例子。希望这能有所帮助

我想出了一个解决方案，允许你使用NSLocalizedString。我创建了一个名为NSBundle+ runtimellanguage的NSBundle类别。界面是这样的。

// NSBundle+RunTimeLanguage.h
#import <Foundation/Foundation.h>
@interface NSBundle (RunTimeLanguage)
#define NSLocalizedString(key, comment) [[NSBundle mainBundle] runTimeLocalizedStringForKey:(key) value:@"" table:nil]
- (NSString *)runTimeLocalizedStringForKey:(NSString *)key value:(NSString *)value table:(NSString *)tableName;
@end

实现是这样的。

// NSBundle+RunTimeLanguage.m
#import "NSBundle+RunTimeLanguage.h"
#import "AppDelegate.h"

@implementation NSBundle (RunTimeLanguage)

- (NSString *)runTimeLocalizedStringForKey:(NSString *)key value:(NSString *)value table:(NSString *)tableName
{
    AppDelegate *appDelegate = (AppDelegate *)[UIApplication sharedApplication].delegate;
    NSString *path= [[NSBundle mainBundle] pathForResource:[appDelegate languageCode] ofType:@"lproj"];
    NSBundle *languageBundle = [NSBundle bundleWithPath:path];
    NSString *localizedString=[languageBundle localizedStringForKey:key value:key table:nil];
    return localizedString;
}
@end

而不是仅仅添加导入NSBundle+RunTimeLanguage.h到使用NSLocalizedString的文件中。

如你所见，我将我的languageCode存储在AppDelegate的属性中。你可以把它存储在任何你想要的地方。

我唯一不喜欢的是一个警告，NSLocalizedString马可重新定义。也许有人能帮我修好这部分。

Swift 3扩展:

extension Locale {
    static var preferredLanguage: String {
        get {
            return self.preferredLanguages.first ?? "en"
        }
        set {
            UserDefaults.standard.set([newValue], forKey: "AppleLanguages")
            UserDefaults.standard.synchronize()
        }
    }
}

extension String {
    var localized: String {

    var result: String

    let languageCode = Locale.preferredLanguage //en-US

    var path = Bundle.main.path(forResource: languageCode, ofType: "lproj")

    if path == nil, let hyphenRange = languageCode.range(of: "-") {
        let languageCodeShort = languageCode.substring(to: hyphenRange.lowerBound) // en
        path = Bundle.main.path(forResource: languageCodeShort, ofType: "lproj")
    }

    if let path = path, let locBundle = Bundle(path: path) {
        result = locBundle.localizedString(forKey: self, value: nil, table: nil)
    } else {
        result = NSLocalizedString(self, comment: "")
    }
        return result
    }
}

用法:

Locale.preferredLanguage = "uk"

label.text = "localizedKey".localized

你可以用你想要做这件事的本地化字符串集构建一个子bundle，然后使用NSLocalizedStringFromTableInBundle()来加载它们。(我假设这是与你可能在应用上做的正常UI本地化分开的内容。)

我想添加对iOS官方不支持的语言的支持(未在系统设置下的语言部分列出)。通过遵循苹果的国际化教程和Brian Webster和geon的一些提示，我想出了这段代码(把它放在main.m中):

int main(int argc, char * argv[]) {
    @autoreleasepool {
        // Grab regional settings locale, for Slovenian this is either sl_SI or en_SI
        NSLocale *locale = [NSLocale currentLocale];
        NSString *ll = [locale localeIdentifier]; // sl_SI

        // Grab the first part of language identifier
        NSArray *comp = [ll componentsSeparatedByString:@"_"];
        NSString *ll1 = @"en";
        if (comp.count > 0) {
            ll1 = comp[0]; // sl, en, ...
        }
        // Check if we already saved language (user can manually change it inside app for example)
        if (![[NSUserDefaults standardUserDefaults] objectForKey:@"SelectedLanguage"]) {
            //   Slovenian (Slovenia),            Slovenia
            if ([ll isEqualToString:@"sl_SI"] || [ll isEqualToString:@"en_SI"]) {
                ll1 = @"sl-SI"; // This is the part of localized path for Slovenian language that Xcode generates
            }
            // Add more unsupported languages here...

            [[NSUserDefaults standardUserDefaults] setObject:ll1 forKey:@"SelectedLanguage"]; // Save language
        }
        else {
            // Restore language as we have previously saved it
            ll1 = [[NSUserDefaults standardUserDefaults] objectForKey:@"SelectedLanguage"];
        }
        // Overwrite NSLocalizedString and StoryBoard language preference
        [[NSUserDefaults standardUserDefaults] setObject:[NSArray arrayWithObjects:ll1, @"en", @"fr", nil] forKey:@"AppleLanguages"];
        // Make sure settings are stored to disk
        [[NSUserDefaults standardUserDefaults] synchronize];

        return UIApplicationMain(argc, argv, nil, NSStringFromClass([AppDelegate class]));
    }
}

这适用于Storyboard和NSLocalizedString代码。该代码假设用户将有一个选项，手动更改应用程序内的语言稍后。

当然，不要忘记添加适当的故事板翻译和本地化。字符串翻译(见链接到上面的苹果页面如何做到这一点)。

也许你应该补充这个(在.pch文件#import后):

extern NSBundle* bundle; // Declared on Language.m

#ifdef NSLocalizedString
    #undef NSLocalizedString
    // Delete this line to avoid warning
    #warning "Undefining NSLocalizedString"
#endif

#define NSLocalizedString(key, comment) \
    [bundle localizedStringForKey:(key) value:@"" table:nil]