swift属性nil在unwindToViewController之外

Question

To pass data between views, I decided to use a "temporary" object that would act as the data model of my views.

var tempMedecine = TempMedecine()
var xValue = 0

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
  if let dmController = segue.destinationViewController as? JRBDosageMainTableViewController {
    dmController.tempMedecine = self.tempMedecine
  }
}

 @IBAction func unwindToViewController(segue: UIStoryboardSegue) {
  if let dosageController = segue.sourceViewController as? JRBDosageMainTableViewController {
    self.tempMedecine = dosageController.tempMedecine!
    self.xValue = 10
    let dosageCell = tableView.cellForRowAtIndexPath(NSIndexPath(forRow: 1, inSection: 0))
    dosageCell?.detailTextLabel?.text = String(self.tempMedecine.dosageQuantity!) + " " + self.tempMedecine.dosageQuantityType!
  }
}

override func shouldPerformSegueWithIdentifier(identifier: String, sender: AnyObject?) -> Bool {
  if identifier == "saveMedecine" {
    print(xValue)
    guard tempMedecine.name != nil else {
      Common.genericAlertController(self, title: "Error", message: "You need to define a name", preferedStyle: .Alert)
      return false
    }
    guard self.tempMedecine.dosageQuantityType != nil else {
      Common.genericAlertController(self, title: "Error", message: "You need to set a quantity", preferedStyle: .Alert)
      return false
    }

    }
    else {
      return true
    }
    return false
}

This is some of my code from the "index" viewController where I need to tackle validation.

As you can see all of my viewControllers have a property named tempMedecine . I pass it around and update the data if needed.

The problem is that self.tempMedecine.dosageQuantityType returns nil in the shouldPerformSegueWithIdentifier method but isn't returning nil in the unwindToViewController method.

I figured there could be two instances of my TempMedecine object, but that's not the case. I also thought there might be a problem with the way I pass the tempMedecine variable between my viewControllers but the property tempMedecine.name is effectively transfered, the only difference is that this property is set in the same viewController where I want to implement validation :

func textFieldShouldReturn(textField: UITextField) -> Bool {
        textField.resignFirstResponder()
        self.tempMedecine.name = textField.text
        return true
}

It's really looking like I'm working with two different scope. As soon as I leave the unwindToViewController method, I would get back to another scope where the tempMedecine variable isn't updated.

But the weird part is when I use a simple variable like xValue . If I update its value in the unwindToViewController method I get the correct value in shouldPerformSegueWithIdentifier

What am I missing? Thanks for your help.

Answer 1

Okay, I fixed it. What happened was that I implemented some code to reset the dataSource which is tempMedecine if the user decided to click on the Back Button in the navigation bar :

if self.isMovingToParentViewController() {
  tempMedecine?.dosageQuantity = nil
  tempMedecine?.dosageQuantityType = nil
}

The thing is, I never thought the issue could come from this as I can use the tempMedecine data to set the value in my tableView after unwinding to the index viewController but I totally missed the part when object are passed my reference.