Preloaded database with Realm Swift - swift

Question

I'm having a little trouble in getting PreLoaded data to work. At first, here is code:
if firstRun {
userDefaults.set(1, forKey: "dayCount")
userDefaults.set(dateFormatter.string(from: date), forKey: "date")
let newPath = defaultPath.deletingLastPathComponent()
let v0Path = bundleURL("default")
do {
//try FileManager.default.removeItem(at: defaultPath)
try FileManager.default.copyItem(at: v0Path!, to:defaultPath)
} catch {
print(error)
}
} ...
v0Path:
file:///Users/dimasalbuquerque/Library/Developer/CoreSimulator/Devices/7FE635BA-AA7A-4241-AF3B-88AD60693AE7/data/Containers/Bundle/Application/B6739B92-B7D8-4DD8-9DA8-CD9BBD84B109/Example.app/default.realm
defaultPath:
file:///Users/dimasalbuquerque/Library/Developer/CoreSimulator/Devices/7FE635BA-AA7A-4241-AF3B-88AD60693AE7/data/Containers/Data/Application/A86C4337-9006-497C-A688-AD781F49EF04/Documents/default.realm
I followed this guide: https://github.com/realm/realm-cocoa/blob/master/examples/ios/swift-2.2/Migration/AppDelegate.swift
Problem is that when the program is running by the first time, it executes the code correctly, but when I try to access realm database, it says it's empty. Although when I open the app for the second time, it works, the data is there. It's already over 1 week that I'm trying to solve this, I've searched through all the net but without success.
Here is where Realm is first called:
class HomeViewController: UIViewController {
#IBOutlet weak var message: UILabel!
#IBOutlet weak var backward: UIButton!
#IBOutlet weak var forward: UIButton!
#IBOutlet weak var background: UIImageView!
#IBOutlet weak var timeBtn: UIButton!
#IBOutlet weak var favoriteBtn: UIButton!
#IBOutlet weak var googleAd: GADBannerView!
let userDefaults = UserDefaults.standard
let realm = try! Realm()
var currentDate = 1
var time = 0 {
didSet {
if time != oldValue {
randomBackground(time)
}
}
}
var dailyMessage: DailyMessagesRealm?
var currentMsg: Message?
override func viewDidLoad() {
super.viewDidLoad()
let first = userDefaults.bool(forKey: "notFirstRun")
if !first {
userDefaults.set(true, forKey: "notFirstRun")
reNew()
}
let day = userDefaults.integer(forKey: "dayCount")
currentDate = day
let empty = realm.objects(DailyMessagesRealm.self).isEmpty
let dailyMessage = realm.objects(DailyMessagesRealm.self).filter("date == '\(day)'").first
//*********Error occurs here***********
self.dailyMessage = dailyMessage!
self.currentMsg = dailyMessage?.morningMessage
self.currentMsg = dailyMessage?.morningMessage
changeMessage((dailyMessage?.morningMessage?.message)!)
initAds()
changeBackground("morning1")
checkFavorite()
} ...

Answer 1

From the sound of it, you must be calling Realm() somewhere before you're performing your copy operation here.
default.realm is only opened when you call Realm() for the first time. Once it's open though, it stores cached information about the file in memory, so if you replace it after the fact, you'll end up with unpredictable behavior.
If you absolutely need to do some kind of operation with Realm(), you can enclose it in an #autoreleasepool { } block to ensure its cached entries in memory are predictably flushed before you do the file copy.
Other than that, I recommended checking your code to ensure you're performing this file copy before touching any instances of Realm() pointing at it.