Realm Swift EXC_BAD_ACCESS During Segue with Unpersisted Object - ios

Question

I've got an app that I've started adding Realm to and I think I must be doing something wrong because I keep running into EXC_BAD_ACCESS when passing unpersisted objects between view controllers.
Here's a stripped down version of my app.
class TodoTask: Object {
dynamic var name: String = ""
let steps = List<Step>()
convenience init(name: String) {
self.init()
self.name = name
}
}
class Step: Object {
dynamic var name: String = ""
convenience init(name: String) {
self.init()
self.name = name
}
}
class TodoListController: UIViewController {
let todos = List<TodoTask>()
override func viewDidLoad() {
super.viewDidLoad()
var t1 = TodoTask(name: "Todo1")
let steps = [
Step("Do this"),
Step("Do that"),
]
t1.steps.appendContentsOf(steps)
var t2 = TodoTask(name: "Todo2")
let steps = [
Step("Do these"),
Step("Do those"),
]
t2.steps.appendContentsOf(steps)
todos.appendContentsOf([t1, t2])
// Display table of todos.
}
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if let detailsController = segue.destinationViewController as? TodoDetailViewController,
let selectedTask = getSelectedTask() {
detailsController.task = selectedTask
}
}
}
class TodoDetailViewController: UIViewController {
var task: TodoTask? // <<< EXC_BAD_ACCESS
// Display the task's steps.
}
Unfortunately, I can't figure out what triggers the EXC_BAD_ACCESS and it happens intermittently. I didn't copy a stacktrace (d'oh!) but I remember it being in the C++ destructor for some sort of Row object. This is odd to me because there doesn't seem to be a database file in my Documents folder.
I'm pretty confident this is a Realm-based error because I experienced no weird crashes until I converted my plain Swift objects to Realm objects.
My only hunch is that I might be using List wrong since the warning This method can only be called during a write transaction. is in the comments of the appendContentsOf method. However, I was under the impression that I could use Realm objects that weren't stored in a Realm just like normal Swift objects.
Am I using Realm objects wrong? Is there anything else I can look into?
I'm on Realm 0.95.2.
Thanks!
Edit:
func getSelectedTask() -> TodoTask? {
if let index = taskTableView.indexPathForSelectedRow {
return tasks[index]
}
return nil
}

Answer 1

The issue is that a Realm List should not be created directly. This class is only used to manage to-many relationships on Object models. Instead, you should use a standard Swift array to store the unpersisted Realm Objects.
So switch:
let todos = List<TodoTask>()
to
let todos = [TodoTask]()