我有一种我无法理解的行为。
我在firebase database上删除了一个节点，在观察.value期间我仍然收到数据。但是在firebase数据库中，该节点将被删除。
我有一个名为users_shoppinglists的节点。以下是要观察存储的用户节点的所有ID。然后我迭代所有的id来观察并调用一个观察每个ID的函数。
当我需要删除列表时，我更新status节点上名为shoppinglists的节点，并通过云功能删除所有与此列表相关的数据。
但观察期间仍然收到数据。我似乎在完全删除之前再次收到数据。
迭代所有id：
func ObserveAllList() -> Void{
if currentUser == nil { return }
self.ShowActivityIndicator()
ref.child("users_shoppinglists").child(currentUser!.id!).observe(.value, with: { (usersListsSnap) in
if usersListsSnap.value is NSNull { self.HideActivityIndicator(); return }
for listSnap in usersListsSnap.children {
let list = listSnap as! DataSnapshot
self.ObserveSingleList(listID: list.key)
}
}) { (error) in
NSLog(error.localizedDescription)
let title = String.OnlineFetchRequestError
let message = error.localizedDescription
self.ShowAlertMessage(title: title, message: message)
return
}
}
调用函数来观察每个ID：
func ObserveSingleList(listID:String) -> Void {
self.ShowActivityIndicator()
ref.child("shoppinglists").child(listID).observeSingleEvent(of: .value, with: { (snapshot) in
if snapshot.value is NSNull { self.HideActivityIndicator(); return }
//Read listData
var newList = ShoppingList()
newList.id = snapshot.key
newList.name = snapshot.childSnapshot(forPath: "listName").value as? String
newList.owneruid = snapshot.childSnapshot(forPath: "owneruid").value as? String
newList.relatedStore = snapshot.childSnapshot(forPath: "relatedStore").value as? String
//Read List items
self.ref.child("listItems").child(listID).observe(.value, with: { (itemSnap) in
var newItems = [ShoppingListItem]()
for items in itemSnap.children {
let item = items as! DataSnapshot
var newItem = ShoppingListItem()
newItem.id = item.key
newItem.listID = listID
newItem.isSelected = item.childSnapshot(forPath: "isSelected").value as? Bool
newItem.itemName = item.childSnapshot(forPath: "itemName").value as? String
newItem.sortNumber = item.childSnapshot(forPath: "sortNumber").value as? Int
newItems.append(newItem)
}
newList.items = newItems
//Read List members
self.ref.child("shoppinglist_member").child(listID).observe(.value, with: { (memberSnap) in
var newMembers = [ShoppingListMember]()
for members in memberSnap.children {
let member = members as! DataSnapshot
var m = ShoppingListMember()
m.memberID = member.key
m.status = member.value as? String
newMembers.append(m)
}
newList.members = newMembers
DispatchQueue.main.async {
if let index = allShoppingLists.index(where: { $0.id == listID }){
allShoppingLists[index] = newList
} else {
allShoppingLists.append(newList)
}
self.HideActivityIndicator()
NotificationCenter.default.post(name: Notification.Name.ShoppingBuddyListDataReceived, object: nil, userInfo: nil)
}
}, withCancel: { (error) in
self.HideActivityIndicator()
NSLog(error.localizedDescription)
let title = String.OnlineFetchRequestError
let message = error.localizedDescription
self.ShowAlertMessage(title: title, message: message)
return
})
}, withCancel: { (error) in
self.HideActivityIndicator()
NSLog(error.localizedDescription)
let title = String.OnlineFetchRequestError
let message = error.localizedDescription
self.ShowAlertMessage(title: title, message: message)
return
})
}) { (error) in
self.HideActivityIndicator()
NSLog(error.localizedDescription)
let title = String.OnlineFetchRequestError
let message = error.localizedDescription
self.ShowAlertMessage(title: title, message: message)
return
}
}
云功能：
//****************************************************************************************************************/
// Handles an action when status value changed in users_shoppinglists node
//****************************************************************************************************************/
exports.handle_ListStatusUpdate = functions.database.ref('/shoppinglists/{listID}').onUpdate(event => {
var listData = event.data.val()
console.log('Status', listData.status)
//handle deleted by owner
if (String(listData.status) == 'deleted by owner') {
//Get all members to delete the list on their users_shoppinglists node
return admin.database().ref('shoppinglist_member').child(event.params.listID).once('value').then(listMember => {
var promises = []
listMember.forEach(function (member) {
promises.push(admin.database().ref('users_shoppinglists').child(member.key).child(event.params.listID).set(null).then(() => {
return admin.database().ref('shoppinglist_member').child(event.params.listID).set(null).then(() => {
// delete the original shopping list
return admin.database().ref('shoppinglists').child(event.params.listID).set(null).then(() => {
return admin.database().ref('listItems').child(event.params.listID).set(null).then(() => {
})
})
})
}))
})
})
}
});/*********************************************************************************************************** */
答案 0 :(得分：0)
在Simulator上遇到此问题。它不仅仅是.value而且.childRemoved和.childChanged根本没有被触发（只有.childAdded正在工作）。
尝试在iPhone上运行。然后我制作了＃34;删除所有内容和设置......＆＃34;到模拟器，它也开始在模拟器上再次工作。
我敢打赌，firebase缓存在开发过程中会变脏，而您在代码中添加或删除观察者，可能会更改数据库中的结构，并且在某些时候它会停止适当的反应。