Swift 中的单例 0 个改进

第一种：

class Singleton {
    let name: String
    init(name: String) {
        self.name = name
    }
}

let singleton = Singleton(name: "iOSCaff")

singleton.name

第二种：

class Singleton {
    static let instance = Singleton(name: "iOSCaff")

    let name: String
    private init(name: String) {
        self.name = name
    }
}

Singleton.instance.name

第三种：

class Singleton {
    private static let instanceManager: Singleton = {
        let shared = Singleton(name: "iOSCaff")
        /// do something...
        return shared
    }()

    let name: String
    private init(name: String) {
        self.name = name
    }

    class func instance() -> Singleton {
        return instanceManager
    }
}

Singleton.instance().name