调用超类上的保护块时，是否有任何方法可以让子类的重写方法返回

Question

Currently I have a super class:

class ShareButtonAction : ButtonAction {
    override func execute() {
        guard let isReachable = reachability?.isReachable() where isReachable == true else {                
            print("No network connection")
        return
    }
}

And a child class of ShareButtonAction:

class ShareTwitterAction : ShareButtonAction {
    override func execute() {
        super.execute()
        guard let isReachable = reachability?.isReachable() where isReachable == true else {
            return
        }
    }

I don't want the child class's implementation of execute to be fired off if the guard condition is caught in the superclass. Currently I have to duplicate code which is bothering me.

Is there a way to tell the child class dont bother executing if the superclass guard is caught.

I know I can fall back to passing blocks and not execute the containing block of the guard fails although I feel like there should be a built in mechanism in swift to make this easier. I am hoping I just have not found it yet.

Answer 1

The built-in mechanisms are either returning a value from the superclass implementation, or throwing an exception there. In a simple case, have the method return a boolean value. The subclass implementation can check the return value from the superclass call.

Answer 2

You could make the method return a boolean value and use that to decide if you want to execute the code in the subclass.

class ShareButtonAction : ButtonAction {

  override func execute() -> Bool {

    guard let isReachable = reachability?.isReachable() where isReachable else {
      print("No network connection")
      return false
    }

    return true
  }

}

class ShareTwitterAction : ShareButtonAction {

  override func execute() -> Bool {
    let result = super.execute()

    if result {
      //... your code here
    }

    return result
  }

}