Object has been deleted or invalidated. (Realm) - swift

Question

Please refer Error: Object has been deleted or invalidated. (Realm)
I encounter this error with both 2 cases also.
I try to find the DBProduct before delete, but it also got Error: Object has been deleted or invalidated. Is this wrong? Please help me. I call this method in block of Alert view as Case 2.
let realm = try! Realm()
try! realm.write {
let dbProduct = realm.objectForPrimaryKey(DBProduct.self, key: product.id)
if dbProduct != nil {
realm.delete(dbProduct!)
}
}
Update: This issue happens on iOS8 only, and it is OK on iOS 9.

Answer 1

Normally, that error should only be thrown if you try and access a property of a Realm object that has been deleted, or if you explicitly told its parent Realm object to invalidate.
Like James said, it's quite likely that your product variable there has already been invalidated, in which case trying to call product.id would likely cause that crash.
If that's the case, then the easiest thing to do to fix this would be to avoid using the product variable and instead, simply making a copy of the value of id directly. This way, if the object is deleted/invalidated, you still have its primary key in which you can test to see if it still exists.
On a side note, this code could certainly be made a bit more efficient as well. It's not necessary to perform queries inside write transactions and you should only open a write transaction if there actually was an object to delete (Write transactions are pretty heavy things, so they should be avoided as much as possible).
let productID = product.id //save a copy of the ID in case 'product' gets deleted.
let realm = try! Realm()
let dbProduct = realm.objectForPrimaryKey(DBProduct.self, key: productID)
if dbProduct != nil {
try! realm.write {
realm.delete(dbProduct!)
}
}
I hope that helped!