Question

我有一个功能，每次有人第一次打开我的项目时，我只想运行一次。如何修复我的代码，使其仅运行一次我的函数，每隔一次将值设置为false。任何解释都会非常有用。

// seedToDataBase()
    var seed = seedToDataBase()
    orderMyAnime()
    do{
    let firstRun = UserDefaults.standard.bool(forKey: seed) as Bool
    if !firstRun {
        //run your function
        seedToDataBase()
        UserDefaults.standard.set(true, forKey: seed)
        }
    }catch {
        print("Unexpected error: \(error).")
    }

这是我正在调用的函数：

func seedToDataBase()
{
    var seedAnime: AnimeObjectMO!
    for o in managedAnime{
        if let appDelegate = (UIApplication.shared.delegate as? AppDelegate){
            seedAnime = AnimeObjectMO(context: appDelegate.persistentContainer.viewContext)
            seedAnime.aName = o.aName
            seedAnime.aRating = o.aRating
            seedAnime.aRanking = o.aRanking
            seedAnime.aDescription = o.aDescription
            //newAnime.aImage = NSData(data: UIImageJPEGRepresentation(UIImage(named: addAnimeImage.text!)!, 1.0)!) as Data!
            seedAnime.aImage = NSData(data: UIImagePNGRepresentation(o.aImage)!) as Data!


            appDelegate.saveContext()
        }
    }
}

Answer 1

try this code when you open the app that time you return false value in userdefault than after call the function            



 let hasLaunchedKey = "CallFunction"
                let defaults = UserDefaults.standard
                var hasLaunched = defaults.bool(forKey: hasLaunchedKey)

                if !hasLaunched {
                    defaults.set(true, forKey: hasLaunchedKey)
                }


        func seedToDataBase()
        {
            var seedAnime: AnimeObjectMO!
            for o in managedAnime{
                if let appDelegate = (UIApplication.shared.delegate as? AppDelegate){
                    seedAnime = AnimeObjectMO(context: appDelegate.persistentContainer.viewContext)
                    seedAnime.aName = o.aName
                    seedAnime.aRating = o.aRating
                    seedAnime.aRanking = o.aRanking
                    seedAnime.aDescription = o.aDescription
                    //newAnime.aImage = NSData(data: UIImageJPEGRepresentation(UIImage(named: addAnimeImage.text!)!, 1.0)!) as Data!
                    seedAnime.aImage = NSData(data: UIImagePNGRepresentation(o.aImage)!) as Data!


                    appDelegate.saveContext()
                }
            }
        }

Answer 2

您的代码几乎正确，只是key部分错误。

您的var seed = seedToDataBase()每次调用时都会生成一个新实例。所以种子不是恒定的，每次都不同，这就是你的代码不起作用的原因。

UserDefault的密钥应该是唯一的，因此您应该编写一些不会更改的String名称，并且不应该将该名称用于其他UserDefault操作。

将您的代码更改为：

// seedToDataBase()
    var seed = seedToDataBase()
    orderMyAnime()
    do{
    let firstRun = UserDefaults.standard.bool(forKey: "SomeKeyName")
    if !firstRun {
        //run your function
        seedToDataBase()
        UserDefaults.standard.set(true, forKey: "SomeKeyName")
        }
    }catch {
        print("Unexpected error: \(error).")
    }

Answer 3

let hasRunAppOnceKey = "hasRunAppOnceKey"
let defaults = UserDefaults.standard
if defaults.bool(forKey: hasRunAppOnceKey) == false {
   // Some code you want to run on first use...
   defaults.set(true, forKey: hasRunAppOnceKey)

} else {
   // Some code you want to run on every other time...
}

如何使用布尔值的用户默认值来检查函数是否已运行？

3 个答案: