Firebase dispatch_async不断使-swift 2 iOS9崩溃

pod update Firebase

DispatchQueue.global(qos: .userInitiated).async {
    // 执行耗时操作
    DispatchQueue.main.async {
        // 更新UI
    }
}

DispatchQueue.global(qos: .userInitiated).async {
    do {
        // 执行可能抛出错误的操作
    } catch {
        print("Error: \(error)")
    }
}

DispatchQueue.global(qos: .userInitiated).async { [weak self] in
    guard let self = self else { return }
    // 使用self进行操作
}

FirebaseApp.configure(options: FirebaseOptions())
FirebaseAnalytics.getInstance().setAnalyticsCollectionEnabled(false)

import Firebase

DispatchQueue.global(qos: .userInitiated).async {
    // 执行耗时操作，例如从Firebase数据库读取数据
    Database.database().reference().child("users").observeSingleEvent(of: .value, with: { snapshot in
        DispatchQueue.main.async {
            // 在主线程上更新UI
            if let userDict = snapshot.value as? [String: AnyObject] {
                let user = User(dictionary: userDict)
                self.updateUI(with: user)
            }
        }
    }) { error in
        print("Error reading data: \(error.localizedDescription)")
    }
}