How do I check if userDefault is empty?

Question

I'm trying to deny access to a certain view controller if the userDefault is empty, but the code doesn't seem to work. To be a bit more clear, I'm saving a favorite-list to a userDefault. This is my code:

 if UserDefaults.standard.array(forKey: "favorites") == nil {

        navigationController?.popToRootViewController(animated: true)
        return
    }

The error is Index out of range, which means that the whole block is ignored (the code after this block runs and since the user default is empty it crashes when trying to retrieve information that isn't there).

The funny thing is, the code works the first time I try to enter the viewController (it denies me access). But if I favorite mark an object (save to userDefault), then un-favorite the same object (userDefault becomes empty), and enter the viewController, the program crashes.

I have tried:

if let favExist = UserDefaults.standard.array(forKey: "favorites") {
        print("")
        print("FAV EXISTS")
        print("")

    }else {
        print("")
        print("NOPE")
        print("")
        navigationController?.popToRootViewController(animated: true)
        return
    }

...and the same problem persists. In print() the log tells me FAV EXISTS after I favorite mark, then un-favorite mark, then try accessing the page (even though the userDefault now should be empty).

I have also tried code from other threads. The suggested code to solve my problem from the other thread was:

let defaults = UserDefaults.standard

    if (!defaults.bool(forKey: "favorites")) {
        defaults.set(true, forKey: "favorites")
    }

I'm not really sure how to implement it though? Where do I use this? And what does it do?

Any idea what's wrong?

Answer 1

It´s enough to do this:

if let favorites = UserDefaults.standard.array(forKey: "favorites") {
     // userDefault has a value
} else {
     // userDefault is nil (empty)
}

Update:
You need to make a check within the if-statement if your arrat has any values too:

if let favorites = UserDefaults.standard.array(forKey: "favorites") {
    print("Favorites exists")

    if favorites.isEmpty {
        print("Favorites is empty")
    } else {
        print("Favorites is not empty, it has \(favorites.count) items")
    }
} else {
    print("Favorites is nil")
}

Answer 2

When you set the UserDefaults Array also set a BOOL to UserDefaults. When you recover the Bool it won't crash even if it hasn't been set.

var favouritesset = UserDefaults.standard.bool(forKey: "favoritesset")

if favouritesset == true {
//Then Recover the Array
var array = UserDefaults.standard.array(forKey: "favorites")
}