Swift中观察者模式观察一个值的变化

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  1. class Obserber {
  2. var name:String?
  3. var count:Int = 0
  4. {
  5. willSet{
  6. print("Will set an new value \(newValue) to count,current count is \(count)")
  7. }
  8. didSet{
  9. print("count changed form \(oldValue) to \(count)")
  10. if count < 10
  11. {
  12. name = "name1"
  13. }else
  14. {
  15. name = "name2"
  16. }
  17. }
  18. }
  19. }
  20. var ob:Obserber = Obserber()
  21. ob.count = 15

输出结果为:

Will set an new value 15 to countcurrent count is 0

count changed form 0 to 15

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