Download as PDF, PPTX
Uploaded byYoungSu Son
Singleton 패턴 (김진영 - EVA, 소마에 10기)
The Singleton pattern ensures that only one instance of a class is created and provides a global access point to that instance. It describes how to implement the concept of a singleton class by creating a private constructor, a static method that returns the instance, and a static property that holds the single instance of the class. The document discusses issues that can arise with thread safety when multiple threads simultaneously try to access the singleton instance and provides solutions like using mutex locking to ensure only one thread initializes the instance.
More Related Content
Similar to Singleton 패턴 (김진영 - EVA, 소마에 10기)
![[NEXT] Android Profiler 사용법](https://cdn.slidesharecdn.com/ss_thumbnails/day6profiler150810-150811041218-lva1-app6892-thumbnail.jpg?width=640&height=640&fit=bounds)
![[NEXT] Flask 로 Restful API 서버 만들기](https://cdn.slidesharecdn.com/ss_thumbnails/flask2-141209115126-conversion-gate02-thumbnail.jpg?width=640&height=640&fit=bounds)
Singleton 패턴 (김진영 - EVA, 소마에 10기)
- 1.
- 2.
- 3.
- 4.
- 5.
- 6.
- 7. object: 0x40012a object: 0x40012a object:0x40012a object: 0x40012a N . . . . . . N ! ?
- 8.
- 9. Singleton (1) • private • staticmInstance • data instance
- 10.
- 11. • s1, s2,s3 add() 3 -> • S1 add() Data: 1 object 0x40012a
- 12. • s1, s2,s3 add() 3 -> • S1 S2 add() add() Data: 1 Data: 2 object 0x40012a object 0x40012a
- 13. • s1, s2,s3 add() 3 -> • S1 S2 S3 add() add() add() Data: 1 Data: 2 Data: 3 object 0x40012a object 0x40012a object 0x40012a
- 14. Thread1 Thread2 Thread3 getInstance()getInstance() getInstance()
- 15. object: 0x400120 Thread1 Thread2Thread3 getInstance() getInstance() getInstance() nullptr ! !
- 16. object: 0x400120 Thread1 object: 0x400120 Thread2Thread3 getInstance() getInstance() getInstance() nullptr ! ! ~
- 17. object: 0x400120 Thread1 object: 0x400120 Thread2 object:0x400128 Thread3 getInstance() getInstance() getInstance() nullptr ! ! ~ nullptr? ! ! ???
- 18. ? ~ Thread1 Thread2 Thread3 mInstance = nullptr Thread1 mInstance= nullptr Thread2 mInstance = nullptr Thread3
- 19. ? ~ Thread1 Thread2 Thread3 mInstance = nullptr Thread1 mInstance= nullptr Thread2 mInstance = nullptr Thread3
- 20. ? ~ Thread1 Thread2 Thread3 mInstance = nullptr Thread1 mInstance= nullptr Thread2 mInstance = nullptr Thread3
- 21. ? ~ Thread1 Thread2 Thread3 mInstance = 0x400120 Thread1 mInstance= nullptr Thread2 mInstance = nullptr Thread3
- 22. ? ~ Thread1 Thread2 Thread3 mInstance = 0x400120 Thread1 mInstance= 0x400120 Thread2 mInstance = nullptr Thread3
- 23. ? ~ Thread1 Thread3 mInstance = 0x400120 Thread1 mInstance= 0x400120 Thread2 mInstance = 0x400128 Thread3 Thread2
- 24. ! getInstance()+8 cmp mInstance,0x0 getInstance()+12 jne getInstance()+20 getInstance()+16 mInstance = new Singleton() getInstance()+20 ret • if cmp Jmp instructure .
- 25. ! getInstance()+8 cmp mInstance,0x0 getInstance()+12 jne getInstance()+20 getInstance()+16 mInstance = new Singleton() getInstance()+20 ret Thread1 Thread3 Thread2 mInstance = nullptr
- 26. Thread1 getInstance()+8 cmp mInstance,0x0 getInstance()+12 jne getInstance()+20 getInstance()+16 mInstance = new Singleton() getInstance()+20 ret Thread1(getInstance()+8) Thread3 Thread2 mInstance = nullptr
- 27. jne instructure getInstance()+8 cmpmInstance, 0x0 getInstance()+12 jne getInstance()+20 getInstance()+16 mInstance = new Singleton() getInstance()+20 ret Thread1(getInstance()+12) Thread3 Thread2 mInstance = nullptr
- 28. mInstance nullptr Thread3 cmp getInstance()+8cmp mInstance, 0x0 getInstance()+12 jne getInstance()+20 getInstance()+16 mInstance = new Singleton() getInstance()+20 ret Thread1(getInstance()+12) Thread3(getInstance()+12) Thread2 mInstance = nullptr
- 29. Thread3 Thread1 getInstance()+8 cmp mInstance,0x0 getInstance()+12 jne getInstance()+20 getInstance()+16 mInstance = new Singleton() getInstance()+20 ret Thread1(getInstance()+16) Thread2 mInstance = 0x400120 Thread3(getInstance()+12)
- 30. mInstance Thread3 getInstance()+8 cmp mInstance,0x0 getInstance()+12 jne getInstance()+20 getInstance()+16 mInstance = new Singleton() getInstance()+20 ret Thread1(getInstance()+20) Thread2 Thread3(getInstance()+16) mInstance = 0x400120 Thread1 mInstance = 0x400128 Thread3
- 31. • race condition mutexthread . • ! Mutex !
- 32. DCL (Double Checked Locking) •Locking , if . -> lock
- 33. DCL (Double Checked Locking) •instance , lock .
- 34. DCL (Double Checked Locking) •Locking thread-safe . instance .
- 35. object: 0x40012a object: 0x40012a object:0x40012a object: 0x40012a object: 0x40012a Only One Object, Same Instance! ~