Firebase＆amp; Swift：获取数据后执行segue

Question

当人们登录我的应用程序时，我会从数据库中获取一些数据：

func DownloadButikker() {
    self.ref?.child("Stores").observe(.childAdded, with: { (snapshot) in
        if let dictionary = snapshot.value as? [String: AnyObject] {
            let store = Store()
            store.Latitude = dictionary["Latitude"]?.doubleValue
            store.Longitude = dictionary["Longitude"]?.doubleValue
            store.Store = dictionary["Store"] as? String
            store.Status = dictionary["Status"] as? String
            stores.append(store)
        }
    })
    self.performSegue(withIdentifier: "LogInToMain", sender: nil)
}

我在所有数据加载完成之前执行segue。有没有办法让观察者完成或检查是否在进行segue之前加载了所有数据？

Answer 1

快速解决方案是您需要在完成异步调用后执行segue 。

func DownloadButikker() {
    self.ref?.child("Stores").observe(.childAdded, with: { (snapshot) in
        if let dictionary = snapshot.value as? [String: AnyObject] {
            let store = Store()
            store.Latitude = dictionary["Latitude"]?.doubleValue
            store.Longitude = dictionary["Longitude"]?.doubleValue
            store.Store = dictionary["Store"] as? String
            store.Status = dictionary["Status"] as? String
            stores.append(store)
        }
        DispatchQueue.main.async {
          self.performSegue(withIdentifier: "LogInToMain", sender: nil)
        }
    })
}

Answer 2

func DownloadButikker(completion: Bool = false) {
    self.ref?.child("Stores").observe(.childAdded, with: { (snapshot) in
        if let dictionary = snapshot.value as? [String: AnyObject] {
            let store = Store()
            store.Latitude = dictionary["Latitude"]?.doubleValue
            store.Longitude = dictionary["Longitude"]?.doubleValue
            store.Store = dictionary["Store"] as? String
            store.Status = dictionary["Status"] as? String
            stores.append(store)
            completion(true)
        }
    })
}


// In your ViewController
func myFunction() {
   DownloadButikker { (hasFinished) in
      if hasFinished { 
         self.performSegue(withIdentifier: "LogInToMain", sender: nil)
      }
   }
}