Method 1
class DemoClass{
//1
class var sharedInstance:DemoClass{
//2
struct Static {
static var onceToken:dispatch_once_t = 0
static var instance:DemoClass? = nil
}
//3
dispatch_once(&Static.onceToken){
// 4
Static.instance = DemoClass()
}
return Static.instance!
}
}
Method 2
// 方法二
class DemoClass2{
//1
class var sharedInstance:DemoClass2{
//2
struct Static {
static let instance = DemoClass2()
}
//3
return Static.instance
}
}
Method 3
// 方法三
class DemoClass3{
class var sharedInstance:DemoClass3{
return sharedInstance3
}
}
private let sharedInstance3 = DemoClass3()
Method 4
class DemoClass4{
static let sharedInstance = DemoClass4()
}
參考
THE RIGHT WAY TO WRITE A SINGLETON
Swift Singleton Design Pattern
