在查看Apple的示例代码时，我发现了这种模式。我不确定Swift是如何处理静态数据的，但这在c#中是线程安全的。我包括了Objective-C互操作的属性和方法。

struct StaticRank {
    static let shared = RankMapping()
}

class func sharedInstance() -> RankMapping {
    return StaticRank.shared
}

class var shared:RankMapping {
    return StaticRank.shared
}

Swift 1.2或更高版本现在支持类中的静态变量/常量。所以你可以使用一个静态常数:

class MySingleton {

    static let sharedMySingleton = MySingleton()

    private init() {
        // ...
    }
}

如果你打算在Objective-C中使用你的Swift单例类，这个设置会让编译器生成适当的Objective-C类头:

class func sharedStore() -> ImageStore {
struct Static {
    static let instance : ImageStore = ImageStore()
    }
    return Static.instance
}

然后在Objective-C类中，你可以像在swift之前那样调用你的单例:

[ImageStore sharedStore];

这只是我的简单实现。

在swift中，你可以通过以下方式创建一个单例类:

class AppSingleton: NSObject {

    //Shared instance of class
    static let sharedInstance = AppSingleton()

    override init() {
        super.init()
    }
}

这里有一个Jack Wu/hpique的嵌套结构实现的单例实现示例，仅供参考。实现还展示了如何进行归档，以及一些附带的功能。我找不到这么完整的例子，希望这能对大家有所帮助!

import Foundation

class ItemStore: NSObject {

    class var sharedStore : ItemStore {
        struct Singleton {
            // lazily initiated, thread-safe from "let"
            static let instance = ItemStore()
        }
        return Singleton.instance
    }

    var _privateItems = Item[]()
    // The allItems property can't be changed by other objects
    var allItems: Item[] {
        return _privateItems
    }

    init() {
        super.init()
        let path = itemArchivePath
        // Returns "nil" if there is no file at the path
        let unarchivedItems : AnyObject! = NSKeyedUnarchiver.unarchiveObjectWithFile(path)

        // If there were archived items saved, set _privateItems for the shared store equal to that
        if unarchivedItems {
            _privateItems = unarchivedItems as Array<Item>
        } 

        delayOnMainQueueFor(numberOfSeconds: 0.1, action: {
            assert(self === ItemStore.sharedStore, "Only one instance of ItemStore allowed!")
        })
    }

    func createItem() -> Item {
        let item = Item.randomItem()
        _privateItems.append(item)
        return item
    }

    func removeItem(item: Item) {
        for (index, element) in enumerate(_privateItems) {
            if element === item {
                _privateItems.removeAtIndex(index)
                // Delete an items image from the image store when the item is 
                // getting deleted
                ImageStore.sharedStore.deleteImageForKey(item.itemKey)
            }
        }
    }

    func moveItemAtIndex(fromIndex: Int, toIndex: Int) {
        _privateItems.moveObjectAtIndex(fromIndex, toIndex: toIndex)
    }

    var itemArchivePath: String {
        // Create a filepath for archiving
        let documentDirectories = NSSearchPathForDirectoriesInDomains(NSSearchPathDirectory.DocumentDirectory, NSSearchPathDomainMask.UserDomainMask, true)
        // Get the one document directory from that list
        let documentDirectory = documentDirectories[0] as String
        // append with the items.archive file name, then return
        return documentDirectory.stringByAppendingPathComponent("items.archive")
    }

    func saveChanges() -> Bool {
        let path = itemArchivePath
        // Return "true" on success
        return NSKeyedArchiver.archiveRootObject(_privateItems, toFile: path)
    }
}

如果你不认识其中的一些函数，这里有一个我一直在使用的小Swift实用程序文件:

import Foundation
import UIKit

typealias completionBlock = () -> ()

extension Array {
    func contains(#object:AnyObject) -> Bool {
        return self.bridgeToObjectiveC().containsObject(object)
    }

    func indexOf(#object:AnyObject) -> Int {
        return self.bridgeToObjectiveC().indexOfObject(object)
    }

    mutating func moveObjectAtIndex(fromIndex: Int, toIndex: Int) {
        if ((fromIndex == toIndex) || (fromIndex > self.count) ||
            (toIndex > self.count)) {
                return
        }
        // Get object being moved so it can be re-inserted
        let object = self[fromIndex]

        // Remove object from array
        self.removeAtIndex(fromIndex)

        // Insert object in array at new location
        self.insert(object, atIndex: toIndex)
    }
}

func delayOnMainQueueFor(numberOfSeconds delay:Double, action closure:()->()) {
    dispatch_after(
        dispatch_time(
            DISPATCH_TIME_NOW,
            Int64(delay * Double(NSEC_PER_SEC))
        ),
        dispatch_get_main_queue()) {
            closure()
    }
}

final class MySingleton {
     private init() {}
     static let shared = MySingleton()
}

那就叫它;

let shared = MySingleton.shared