Passing an NSManagedObject Effectively through Storyboard

问题

I have quite a complicated setup in my app that involves an embedded UISplitViewController which feeds a bunch of UIViewControllers.

What I am needing to do is pass an NSManagedObject through the embedded UISplitViewController so I can access it in my separate detail' UIViewControllers.

I have attached an image of my storyboard with some awesome annotations....

This is my prepareForSegue function at the minute, this is in the View Controller where I already have my NSManagedObject, I am looking to pass it to the first SurveyViewController so it can get passed on:

  override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {

    println("Sender is \(sender)")

    if segue.identifier == SurveyIdentifier {


//            let nav : UINavigationController = segue.destinationViewController as! UINavigationController
//            let itemVC: BACUploaderViewController =  nav.topViewController as! BACUploaderViewController

        let surveyViewController: SurveyViewController = segue.destinationViewController as! SurveyViewController


        println("survey view controller: \(surveyViewController)")


//            if let destination = segue.destinationViewController as? MasterViewController {
//                
//                destination.workItem = sender as? Work

//            }
      }

}

I am fairly sure that I have to access my MasterViewController from here by drilling down through the View Hierarchy, but not sure on how to achieve this effectively?

On a side note, the segue does work, I am presented with the correct views, but it pushes the view onto the screen twice and I'm not sure why, I can upload a gif of this if seeing what I am talking about in action might make more sense?

回答1:

You can "reach down" through the hierarchy of view controllers, to get a reference to the table view controller titled "Sections" in the storyboard.

From prepareForSegue in your SurveyViewController:

    // the destination of the "embed" segue will be the split view controller
    let splitVC : UISplitViewController = segue.destinationViewController as! UISplitViewController
    // in a UISplitViewController, viewControllers[0] represents the Master view controller
    // in your case that is a UINavigationController...
    let navVC: UINavigationController =  splitVC.viewControllers[0] as! UINavigationController
    // In a UINavigationController, topViewController represents the visible VC
    // In your case that's the Sections table view controller...
    let sectionsVC : SectionsViewController = navVC.topViewController as! SectionsViewController
    // (replace "SectionsViewController" with the correct class name)
    sectionsVC.object = yourNSManagedObject

This passes the object to the Sections view controller. You can pass the object to the final VCs (the bad boys!) in the prepareForSegue of the Sections view controller. You can't do it earlier, because they are not instantiated before then.

As to why the view might be pushed onto screen twice, my only guess is that you might be using performSegueWithIdentifier from within didSelectRowAtIndexPath of a table view, when the segue is also linked directly to the prototype cell.

回答2:

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {

println("Sender is \(sender)")

if segue.identifier == SurveyIdentifier {


//            let nav : UINavigationController = segue.destinationViewController as! UINavigationController
//            let itemVC: BACUploaderViewController =  nav.topViewController as! BACUploaderViewController

    let surveyViewController: SurveyViewController = segue.destinationViewController as! SurveyViewController
***********************
    surveyViewController.managedObject = self.managedObjectContext
 ************************
//            if let destination = segue.destinationViewController as? MasterViewController {
//                
//                destination.workItem = sender as? Work

//            }
  }

}

You can have an optional named managedObject in your SurveyViewController and then inject your managedObjectContext object from MasterViewController to SurveyViewController. This code snippet is written keeping in mind that you are in MasterViewController

来源：https://stackoverflow.com/questions/32333689/passing-an-nsmanagedobject-effectively-through-storyboard

标签

ios

iphone

swift

core-data

uiviewcontroller