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

这个函数将尝试获取当前语言的本地化字符串，如果没有找到，它将使用英语语言获取它。

- (NSString*)L:(NSString*)key
{
    static NSString* valueNotFound = @"VALUE_NOT_FOUND";
    static NSBundle* enBundle = nil;

    NSString* pl = [NSLocale preferredLanguages][0];
    NSString* bp = [[NSBundle mainBundle] pathForResource:pl ofType:@"lproj"];
    NSBundle* b = [NSBundle bundleWithPath:bp];

    NSString* s = [b localizedStringForKey:key value:valueNotFound table:nil];
    if ( [s isEqualToString:valueNotFound] ) {
        if ( !enBundle ) {
            bp = [[NSBundle mainBundle] pathForResource:@"en" ofType:@"lproj"];
            enBundle = [NSBundle bundleWithPath:bp];
        }
        s = [enBundle localizedStringForKey:key value:key table:nil];
    }

    return s;
}

你觉得Swift 3的这个解决方案怎么样?

extension String {

    func localized(forLanguage language: String = Locale.preferredLanguages.first!.components(separatedBy: "-").first!) -> String {

        guard let path = Bundle.main.path(forResource: language == "en" ? "Base" : language, ofType: "lproj") else {

            let basePath = Bundle.main.path(forResource: "Base", ofType: "lproj")!

            return Bundle(path: basePath)!.localizedString(forKey: self, value: "", table: nil)
        }

        return Bundle(path: path)!.localizedString(forKey: self, value: "", table: nil)
    }
}

简单的用法:

"report".localized(forLanguage: "pl") //forced language
"report".localized() //default language selected by user in settings, in case when your app doesnt support selected lanaguage, the default one is selected, here is an english.

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

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]

如前所述，只要做:

[[NSUserDefaults standardUserDefaults] setObject: [NSArray arrayWithObjects:@"el", nil] forKey:@"AppleLanguages"];

但是为了避免不得不重新启动应用程序，请将该行放在main的main方法中。m，就在UIApplicationMain(…)之前。