Swift safe unwrapping optional a Class Constant without redundancy

Question

I am trying to get more Structure into my code so I am implementing this UserDefaultsService:

class UserDefaultsService {
    
    let defaults = UserDefaults(suiteName: UserDefaults.Keys.groupKey)

    static let shared = UserDefaultsService()
    
    func updateDataSourceArrayWithWishlist(wishlist: Wishlist) {
        guard var dataSourceArray = defaults?.getDataSourceArray() else { return }
        if let index = dataSourceArray.firstIndex(where: ({$0.id == wishlist.id})) {
            dataSourceArray[index] = wishlist
            defaults?.setDataSourceArray(data: dataSourceArray)
        }
    }
    
    func getDataSourceArray() -> [Wishlist]? {
        return defaults?.getDataSourceArray()
    }
}

But as you can see defaults is optional. I know I could safe unwrap it with guard for example everytime I am using it but isn' there some better/cleaner way to do this? What I am thinking is to only unwrap it once and then I can use it everywhere in UserDefaultsService.

You can force unwrap (`!`), but typically what I like to do is to use `guard` to conditionally unwrap or fail with `preconditionFailure` — New Dev, Jan 28 '21 at 15:12
@NewDev that is what I want to to but I can not use `guard` in a class variable — Chris, Jan 28 '21 at 15:14
you can use a computed property. Or, you can use an immediately executed closure, i.e. `let default = { guard let ... }()` — New Dev, Jan 28 '21 at 15:16

score 1 · Accepted Answer · answered Jan 28 '21 at 15:10

1

Add ! end of it's declaration

let defaults = UserDefaults(suiteName: UserDefaults.Keys.groupKey)!

answered Jan 28 '21 at 15:10

Shehata Gamal

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But that could crash – Chris Jan 28 '21 at 15:13
1

? but if `UserDefaults(suiteName: UserDefaults.Keys.groupKey)` is nil? And I force unwrap it ? why cant it crash? – Chris Jan 28 '21 at 15:16
the above line will create the suite defaults if not exists and link to it if exists no crashes here only make sure you have a group with the used name so your data is accessed in extensions – Shehata Gamal Jan 28 '21 at 15:16
huh, I did not know that.. why is it optional then? Anyway, you answered it. Thanks – Chris Jan 28 '21 at 15:18
try it yourself and it won't crash with any constant – Shehata Gamal Jan 28 '21 at 15:21
I believe you :D its just not the expected behavior imo – Chris Jan 28 '21 at 15:22

Swift safe unwrapping optional a Class Constant without redundancy

1 Answers1