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Swift でシングルトン

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Swift 1.2 からはもっと簡単に書けるようになりました。 (2015-04-17)

dispatch_once を使ったシングルトンクラスを Swift に移植する。
static の初期化は dispatch_once を勝手にやってくれるようです。
コードが短い、ステキー。

class var sharedController : FooController
{
    struct Singleton {
        static let instance = FooController()
    }
    return Singleton.instance
}

相当する Objective-C のコード。

+ (FooController *)sharedController
{
    static dispatch_once_t token;
    static FooController *instance = nil;

    dispatch_once(&token, ^{
        instance = [[FooController alloc] init];
    });

    return instance;
}

-
追記: @takabosoft さん @hetima さんのツッコミを受けて、Swiftのシングルトンコードを簡略化しました。dispatch_onceはわざわざ書く必要ないようです。

--
- cf. dispatch_once singleton model in swift -Stack Overflow

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