CODEWITHSUNDEEP
ioscore-dataswiftnsmanagedobject
Steve Marshall
Steve Marshall

Reputation: 8149

How to assign a subclassed NSManagedObject to a var (as opposed to a constant) in swift

I've got an instance variable array of full of Juice objects that is subclassed from NSManagedObject, retrieved from an NSFetch.

I set the UITableViewCell title like this, with no problem:

let currentJuice = juiceList[indexPath.row]

cell.text = currentJuice.name

However, I'm trying to pass an instance of Juice between view controllers. I declare an instance variable var selectedJuice = Juice() variable and then in the willSelectRowAtIndexPath I put:

 selectedJuice = juiceList[indexPath.row]

This line throws the error CoreData: error: Failed to call designated initializer on NSManagedObject class and I can't figure out why! I also don't know how to implement the designated init method in the Juice class, if anyone can help with that one

Upvotes: 2

Views: 405

Answers (1)

Martin R
Martin R

Reputation: 539805

The problem is that Juice() creates a Juice object without using the designated initialiser of NSManagedObject. And actually you don't need to assign a default value to the property at all.

You should declare the property as an optional

var selectedJuice : Juice? // (1)

or implicitly unwrapped optional 

var selectedJuice : Juice! // (2)

Then assigning 

selectedJuice = juiceList[indexPath.row]

should work without problem.

In the first case (1), you would access the property as

if let theJuice = selectedJuice {
    // ...
} else {
    // no Juice selected
}

In the second case (2), you would access the property simple as selectedJuice, and you get a runtime exception if it is not set (nil).

Upvotes: 5

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