swift – 可选闭包,并检查它是否为nil

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所以我想要的是一个类,可能会得到一个闭包传递给它在一个函数,它也可能在某些时候想忽略一个闭包。如何检查闭包变量是否设置和hwo可以删除它,当我完成它?

Cannot invoke ‘!=’ with an argument list of type ‘(@lvalue (sucsess:
Bool!,products: [AnyObject]!) -> ()?,NilLiteralConvertible)’ Type
‘(sucsess: Bool!,products: [AnyObject]!) -> ()?’ does not conform to
protocol ‘NilLiteralConvertible’

  1. class someClass{
  2. //typealias completionHandlerClosureType = (sucsess:Bool!,items:[AnyObject]!)->()
  3. var completionHandler:(sucsess:Bool!,items:[AnyObject]!)->()?
  4. var hitpoints = 100
  5. var someset = ["oh no!","avenge me!"]
  6. init(){}
  7.  
  8. func getHitFunc(impact:Int,passedCompletionsHandler:(sucsess:Bool!,items:[AnyObject]!)->()){
  9. completionHandler = passedCompletionsHandler
  10. hitpoints = hitpoints - impact
  11. }
  12.  
  13. func checkIfDead{
  14. if hitpoints<=0 { // The error received
  15. if completionHandler != nil{// Cannot invoke '!=' with an argument list of type
  16. //'(@lvalue (sucsess: Bool!,NilLiteralConvertible)'
  17. //run the handler if dead
  18. completionHandler(sucsess: true,items: someset)
  19. //do not run it again
  20. completionHandler = nil //Type '(sucsess: Bool!,products: [AnyObject]!) -> ()?' does not conform to protocol 'NilLiteralConvertible'
  21. }
  22. }
  23. else{
  24. completionHandler = nil //Type '(sucsess: Bool!,products: [AnyObject]!) -> ()?' does not conform to protocol 'NilLiteralConvertible'
  25. }
  26. }
  27. }
你需要在括号中包装你的闭包签名,使闭包本身是可选的。现在写的方式,闭包返回一个可选的Void(这不是真的有意义)。
  1. var completionHandler: ((sucsess:Bool!,items:[AnyObject]!)->())?

您的示例代码的一些样式点和修订版本:

  1. // Capitalize class names so it's clear what's a class
  2. class SomeClass {
  3. // "success" has two "c"s
  4. var completionHandler: ((success:Bool!,items:[AnyObject]!)->())?
  5. var hitpoints = 100
  6. var someset = ["oh no!","avenge me!"]
  7.  
  8. init() { }
  9.  
  10. func getHitFunc(impact:Int,passedCompletionsHandler:(success:Bool!,items:[AnyObject]!)->()){
  11. completionHandler = passedCompletionsHandler
  12. hitpoints = hitpoints - impact
  13. }
  14.  
  15. // You were missing the argument list here:
  16. func checkIfDead() {
  17. if hitpoints <= 0 {
  18.  
  19. // Rather than checking to see if the completion handler exists,you can
  20. // just call it using optional Syntax like this:
  21. completionHandler?(success: true,items: someset)
  22. }
  23. completionHandler = nil
  24. }
  25. }

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