相关疑难解决方法(0)

我经常这样做,

let when = DispatchTime.now() + 2.0
DispatchQueue.main.asyncAfter(deadline: when) {
   beep()
}

在一个应用程序中,我们经常这样做

tickle.fresh(){
    msg in
    paint()
}

但如果你做这个

let when = DispatchTime.now() + 2.0
DispatchQueue.main.asyncAfter(deadline: when) {
   tickle.fresh(){
      msg in
      paint()
   }
}

当然,你必须做这个

let when = DispatchTime.now() + 2.0
DispatchQueue.main.asyncAfter(deadline: when) { [weak self] _ in
   tickle.fresh(){
      msg in
      self?.paint()
   }
}

或者,也许这个

let when = DispatchTime.now() + 2.0
DispatchQueue.main.asyncAfter(deadline: when) {
   tickle.fresh(){
      [weak self] msg in
      self?.paint()
   }
}

或许这个

let when = DispatchTime.now() …

如果我有一个闭包传递给这样的函数:

 someFunctionWithTrailingClosure { [weak self] in
     anotherFunctionWithTrailingClosure { [weak self] in 
         self?.doSomething()
     }
 }

如果我[weak self]在someFunctionWithTrailingClosure自己的捕获列表中声明自己没有重新声明它weak再次在捕获列表中anotherFunctionWithTrailingClosure self已经成为一种Optional类型但是它也成为一个weak参考？

谢谢!