Realm accessed from incorrect thread - Swift 3

Question

At the top of my UITableViewController is the following:

let queue = DispatchQueue(label: "background")

When a task is deleted, the following executes:

self.queue.async {
    autoreleasepool {
        let realm = try! Realm()
        realm.beginWrite()
        realm.delete(task)
        do {
            try realm.commitWrite()
        } catch let error {
            self.presentError()
        }
    } 
 }

And then I receive the error

terminating with uncaught exception of type realm::IncorrectThreadException: Realm accessed from incorrect thread.

How could I fix this?

Answer 1

It seems like the write is happening on a different thread than the object was originally accessed from. You should be able to fix it by passing task's id and using that to fetch it from the database right before you do the write (inside the async block).

So at the top:

var taskId = 0  // Set this accordingly

and then something like

self.queue.async {
    autoreleasepool {
        let realm = try! Realm()
        let tempTask = // get task from Realm based on taskId
        realm.beginWrite()
        realm.delete(tempTask)
        do {
            try realm.commitWrite()
        } catch let error {
            self.presentError()
        }
    } 
 }