观察者，动作监听者，iOS Swift中的KVO

Question

Okay, I have an issue with the addObserver function in Swift. How is that possible, if I change a value of an object A that object B reacts? (Without A knows B but B has a variable with a reference to A)

for example here:

class A {
var willChange: Int = 0

// if something happened -> willChange = 1
}

class B {
  let someThing = A()

  //Something like this maybe but i don't really want to check, just get a notice
  if someThing.willChange != 0 {
  }

  func whatEver() {
  //called if willChange is changed
  ...
  }
}

Not only if willChange changed it has to be notificated, just if anything i want happened in A -> notificate B. Thinking of Observer Pattern, but maybe can someone explain if possible with this.

Answer 1

Something like this:

 class A { weak var observer : AnyObject? var willChange: Int = 0{ didSet{ if let bObject = observer as? B{ bObject.whatEver() } } } } class B { let someThing = A() someThing.observer = self func whatEver() { //called if willChange is changed ... } }