swift 单例的几种形式

class func shareInstance() -> Team {
struct TeamStatic{
static let staticInstance = Team()
}
return TeamStatic.staticInstance
}

private let _SingletonASharedInstance = Team()
class func shareInstance1() -> Team {
return _SingletonASharedInstance
}

class var sharedInstance : Team{
        struct Static {
            static let instance:Team = Team()
        }
        return Static.instance
    }

class var sharedInstance1:Team {
var predicate:dispatch_once_t = 0
struct Static1 {
static var onceToken:dispatch_once_t = 0
static var instance:Team?
}
dispatch_once(&Static1.onceToken, { () -> Void in
Static1.instance = Team()
})
return Static1.instance!
}