// 本地化字符串宏定义，key:需要国际化的字符串，comment：一个注释，一般设置为nil
#define NSLocalizedString(key, comment)

// 举例
self.title = NSLocalizedString(@"钱包", nil);

// Localizable.strings 文件中
 // Assets
"profile_banner" = "profile_banner_en";
"profile_banner" = "profile_banner_hant";

// 使用示例，这里只需要进行图片名称的字符串替换即可
UIImage *img = [UIImage imageNamed:NSLocalizedString(@"profile_banner", nil)];

### xxxViewModel.m 文件

#define kUserDefaults       [NSUserDefaults standardUserDefaults]

// 1. 切换语言入口方法
- (void)switchLanguageWithType:(WLTLanguageType)languageType{
    
    if (languageType == self.currentLanguageType) {
        return;
    }
    
    self.currentLanguageType = languageType;
    NSString *lanCode = nil;

    switch (languageType) {
        case WLTLanguageTypeFollowSystem:
            lanCode = nil;
            break;
        case WLTLanguageTypeSimplified:
            lanCode = @"zh-Hans";	//中文简体
            break;
        case WLTLanguageTypeTraditional:
            lanCode = @"zh-Hant";	// 中文繁体
            break;
        case WLTLanguageTypeEnglish:
            lanCode = @"en";		// 英文
            break;
    }
    
    // 切换语言
    [self setUserLanguage:lanCode];
    
    // 刷新keyWindow
    [kWLTAppDelegate resetKeyWindowRootViewController];
}

// 切换语言
// 注释：这里需要将用户选择的语言类型进行本地缓存，系统在加载国际化语言bundle的时候会
// 根据这个值来加载语言版本的
- (void)setUserLanguage:(NSString *)userLanguage{
    //跟随手机系统
    if (!userLanguage.length) {
        [self resetSystemLanguage];
        return;
    }
    
    //用户自定义
    [kUserDefaults setObject:userLanguage forKey:WLTUserLanguageKey];
    [kUserDefaults setObject:@[userLanguage] forKey:@"AppleLanguages"];
    [kUserDefaults synchronize];
}

+ (NSString *)userLanguage{
    return [kUserDefaults objectForKey:WLTUserLanguageKey];
}

+ (NSString *)systemLanguage{
    return [[kUserDefaults objectForKey:@"AppleLanguages"] firstObject];
}

/// 重置系统语言
- (void)resetSystemLanguage{
    [kUserDefaults removeObjectForKey:WLTUserLanguageKey];
    [kUserDefaults setObject:nil forKey:@"AppleLanguages"];
    [kUserDefaults synchronize];
}

### AppDelegate.m 文件

- (void)resetKeyWindowRootViewController{
    
    WLTMainViewModel *mainVm = [WLTMainViewModel viewModel];
    mainVm.tabBarSelectedIndex = 3; //注释：这里要提前设置为“语言切换控制器”相应的tabbarIndex
    WLTMainViewController *newMainVc = [[WLTMainViewController alloc] initWithViewModel:mainVm];

    WLTLanguageViewController *lanVc = [[WLTLanguageViewController alloc] initWithViewModel:[WLTLanguageViewModel viewModel]];
    lanVc.hidesBottomBarWhenPushed = YES;  //注释：如果“语言切换控制器”不是导航控制器的根控制器时，需要提前设置tabbar隐藏

    dispatch_async(dispatch_get_main_queue(), ^{
        // 给出友好提示...
        [MBProgressHUD showActivityWithStatus:NSLocalizedString(@"语言切换中...", nil)];
        
        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(1.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
            [MBProgressHUD hideHUD];
            
            // 重置keyWindow，会初始化整个UI
            self.mainVC = newMainVc;
            self.window.rootViewController = newMainVc;
            
            // 跳转到语言设置页，很关键的一步，让用户不会感知到UI的刷新
            WLTNavigationController *currentNav = newMainVc.tabBarController.selectedViewController;
            NSMutableArray *navVcs = currentNav.viewControllers.mutableCopy;
            [navVcs addObject:lanVc];
            
            currentNav.viewControllers = navVcs;
        });
    });
}

### NSBundle+WLTUtils.m 文件中

// 子类的定义
@interface WLTBundle : NSBundle

@end

@implementation NSBundle (WLTUtils)

// 处理应用内国际化语言切换
+ (void)load{
    
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        
        // 修改 mainBundle 是所属类为"WLTBundle"类
        // mainBundle -> NSBundle  修改为： mainBundle -> WLTBundle -> NSBundle
        object_setClass([NSBundle mainBundle], [WLTBundle class]);
    });
}

+ (NSString *)currentLanguage{
    return [WLTLanguageViewModel userLanguage];
}

@end

@implementation WLTBundle
// 覆写本地化关键发放，进行自定义操作
- (NSString *)localizedStringForKey:(NSString *)key value:(NSString *)value table:(NSString *)tableName{
    
    if ([WLTBundle wlt_mainBundle]) {
        return [[WLTBundle wlt_mainBundle] localizedStringForKey:key value:value table:tableName];
    } else {
        return [super localizedStringForKey:key value:value table:tableName];
    }
}

+ (NSBundle *)wlt_mainBundle{
    
    if ([NSBundle currentLanguage].length) {
        
        NSString *path = [[NSBundle mainBundle] pathForResource:[NSBundle currentLanguage] ofType:@"lproj"];
        if (path.length) {
            return [NSBundle bundleWithPath:path];
        }
    }
    
    return nil;
}

@end