Question

我有2个引用（对于相同的路径），一个用于侦听挂起的订单，另一个用于侦听已完成的订单。全部用于特定位置，用户可以更改。

我现在使用的机制是：

创建一个存储Firebase参考的数组
在我observe待处理订单的事件之前，将Firebase引用推送到我的数组
在我observe完成订单的事件之前，将Firebase引用推送到我的数组
当用户切换其位置时，删除阵列中所有引用的所有观察者。清空阵列并开始在新位置（步骤2和3）中侦听待处理/已完成的订单

我的代码如下所示：

struct Firebase {

  private let ORDERS_PATH = "locations-orders"

  private static var references = [FIRDatabaseReference]()

  static func observePendingOrders(lId: String, f: @escaping (AppState.Order) -> () ) {
    print("observing orders for \(ORDERS_PATH)/\(lId)")

    let pendingOrdersReference = FIRDatabase.database().reference(withPath: "\(ORDERS_PATH)/\(lId)")
    self.references.append(pendingOrdersReference)

    pendingOrdersReference
      .child(dateKeyToday())
      .queryOrdered(byChild: "created_at")
      .observe(.childAdded, with: { firebaseSnapshot in
        ...

        print("order received for \(ORDERS_PATH)/\(lId)")
      }
    )
  }

  static func fetchCompletedOrders(lId: String, f: @escaping ([AppState.Order]) -> () ) {
    print("observing completed orders for \(lId)")

    let completedOrdersReference = FIRDatabase.database().reference(withPath: "\(ORDERS_PATH)/\(lId)")
    self.references.append(completedOrdersReference)

    completedOrdersReference
      .child(dateKeyToday())
      .queryOrdered(byChild: "status_updated_at")
      .observe(.value, with: { firebaseSnapshot in
        ...
      }
    )
  }

  static func removeAllOrderObservers() {
    for reference in references {
      print("removing reference \(reference)")
      reference.removeAllObservers()
    }
    self.references = []
  }

}

然而，当我记录我正在观看的订单的位置时，看起来即使我切换位置后，旧的观察者仍在监听订单。这是我的日志：

observing orders for locations-orders/9RC4H9ZAE457E // first location
observing completed orders for 9RC4H9ZAE457E
removing reference https://mydb-123.firebaseio.com/locations-orders/9RC4H9ZAE457E // switch locations, remove all existing observers for location 9RC4H9ZAE457E
removing reference https://mydb-123.firebaseio.com/locations-orders/9RC4H9ZAE457E
observing orders for locations-orders/1JS53G0TT5ZQD // start listening for orders in new location. notice the new id: 1JS53G0TT5ZQD
observing completed orders for 1JS53G0TT5ZQD
order received for locations-orders/9RC4H9ZAE457E // <-- why is this still showing up?
order received for locations-orders/1JS53G0TT5ZQD
order received for locations-orders/1JS53G0TT5ZQD
order received for locations-orders/9RC4H9ZAE457E // <-- and this one too??
order received for locations-orders/1JS53G0TT5ZQD
order received for locations-orders/1JS53G0TT5ZQD

===更新=== 我甚至试过手柄，它没有工作：

struct Firebase {

  private static var handles = [UInt]()
  private static var references = [FIRDatabaseReference]()

  static func observePendingOrders(lId: String, f: @escaping (AppState.Order) -> () ) {
    print("observing orders for \(ORDERS_PATH)/\(lId)")

    let pendingOrdersReference = FIRDatabase.database().reference(withPath: "\(ORDERS_PATH)/\(lId)")
    self.references.append(pendingOrdersReference)

    let handle = pendingOrdersReference
      .child(dateKeyToday())
      .queryOrdered(byChild: "created_at")
      .observe(.childAdded, with: { firebaseSnapshot in
        ...
      }
    )

    handles.append(handle)
  }

  static func fetchCompletedOrders(lId: String, f: @escaping ([AppState.Order]) -> () ) {
    print("observing completed orders for \(ORDERS_PATH)/\(lId)")

    let completedOrdersReference = FIRDatabase.database().reference(withPath: "\(ORDERS_PATH)/\(lId)")
    self.references.append(completedOrdersReference)

    let handle = completedOrdersReference
      .child(dateKeyToday())
      .queryOrdered(byChild: "status_updated_at")
      .observe(.value, with: { firebaseSnapshot in
        ...
      }
    )
    handles.append(handle)
  }

  static func removeAllOrderObservers() {
//    for reference in references {
//      print("removing reference \(reference)")
//      reference.removeAllObservers()
//    }
//    
    if !references.isEmpty {
      let ref = references[0]
      for handle in handles {
        print("removing handle \(handle)")
        ref.removeObserver(withHandle: handle)
      }
      self.references = []
    }
  }
}

Answer 1

我想我可能已经修好了吗？所以这是因为我实际上正在观察该引用的子节点，因此删除父节点的所有观察者都没有做任何事情，因为你必须在你正在观察的特定节点上删除它。

let pendingOrdersReference = FIRDatabase
  .database()
  .reference(withPath: "\(ORDERS_PATH)/\(lId)")
  .child(dateKeyToday()) // <---- added this thing

这是我的最终解决方案，似乎有效：

struct Firebase {
  private static var references = [FIRDatabaseReference]()

  static func observePendingOrders(lId: String, f: @escaping (AppState.Order) -> () ) {
    print("observing orders for \(ORDERS_PATH)/\(lId)")

    let pendingOrdersReference = FIRDatabase
      .database()
      .reference(withPath: "\(ORDERS_PATH)/\(lId)")
      .child(dateKeyToday())
    self.references.append(pendingOrdersReference)

    ...
  }

  static func fetchCompletedOrders(lId: String, f: @escaping ([AppState.Order]) -> () ) {
    print("observing completed orders for \(ORDERS_PATH)/\(lId)")

    let completedOrdersReference = FIRDatabase
      .database()
      .reference(withPath: "\(ORDERS_PATH)/\(lId)")
      .child(dateKeyToday())
    self.references.append(completedOrdersReference)

    ...

  }

  static func removeAllOrderObservers() {
    for reference in references {
      print("removing reference \(reference)")

      reference.removeAllObservers()
    }
    self.references = []
  }

}

Firebase + Swift：removeAllObservers不工作？

1 个答案: