将一个ViewController中的managedObjectContext传递给Swift中的另一个ViewController？

Question

My current project is a Core Data project in Swift that creates notes. I'm trying to set the managedObjectContext of my destinationVC from the currentVC in prepareForSegue and I am trying to figure out how to do that in Swift.

I've used Apple's "canned code" for setting up a CoreData project in Swift. The CoreData stack is set up in AppDelegate.swift .

At present, I created a method to generate dummy notes in the AppDelegate if there are no notes in the managed object context. That works.

The initial view when the app opens is a Master-Detail VC set up that displays the objects in my managed object context. That works. I can click on a note and it displays on the DetailViewController. This is mostly "canned" code Xcode creates when I started the project.

I created a UIBarButtonItem "Add" button on the MasterViewController , but I can't figure out how to pass the MasterVC 's managedObjectContext to the destinationViewController . When I click that it segues as it should to the DetailViewController .

Here are the properties from my MasterVC :

var detailViewController: DetailViewController? = nil
var addNoteViewController:AddNoteViewController? = nil  // I added this
var managedObjectContext: NSManagedObjectContext? = nil

This is my prepareForSegue method in the MasterViewController .

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
    if segue.identifier == "showDetail" {
        if let indexPath = self.tableView.indexPathForSelectedRow() {
            let object = self.fetchedResultsController.objectAtIndexPath(indexPath) as! NSManagedObject
            let controller = (segue.destinationViewController as! UINavigationController).topViewController as! DetailViewController
            controller.detailItem = object
            controller.navigationItem.leftBarButtonItem = self.splitViewController?.displayModeButtonItem()
            controller.navigationItem.leftItemsSupplementBackButton = true
        }
    }

    if segue.identifier == "addNote" {
        println("segue.identifier is addNote")
        // I think I need to add stuff here so the destination VC "sees" the managedObjectContext
    }
}

I think I also need to add a property on the AddNoteVC that the MasterVC 's prepareForSegue can set. So how do I do that in Swift?

Answer 1

To add a property to your AddNoteViewController , just add a var :

import CoreData

class AddNoteViewController: UIViewController {

    var managedObjectContext : NSManagedObjectContext?

Then you can set this property in your segue:

if segue.identifier == "addNote" {
    println("segue.identifier is addNote")
    // I think I need to add stuff here so the destination VC "sees" the managedObjectContext

    let controller = (segue.destinationViewController as! UINavigationController).topViewController as! AddNoteViewController
    controller.managedObjectContext = managedObjectContext
}

Answer 2

Mystery solved:

I added this line of code to the AddNoteViewController , nothing in prepareForSegue in MasterViewController.swift

let managedObjectContext = (UIApplication.sharedApplication().delegate as! AppDelegate).managedObjectContext