我环顾四周，我无法弄清楚这一点。
如果Firebase快照返回 nil
，我正尝试设置tableView Cell的默认值示例：
创建快照以显示Firebase数据库中的所有事件名称 在tableView中使用dequeReusableCell。
但如果快照返回nil ，则tableView将返回1个单元格，其标签上写着“抱歉，没有事件。”
这是我的firebase快照代码。如果快照使用 print（）语句返回nil，则此代码当前会处理。
func populateTableView(){
let uid = Auth.auth().currentUser?.uid
ref = Database.database().reference()
ref.child("events").child(uid!).child(currentDate).observeSingleEvent(of: .value, with: { (snapshot) in
self.events = []
if let snapshot = snapshot.children.allObjects as? [DataSnapshot] {
for snap in snapshot {
//print("SNAP: \(snap)")
if let postDict = snap.value as? Dictionary<String, AnyObject> {
let key = snap.key
let event = Event(postKey: key, postData: postDict)
self.events.append(event)
//print(self.events)
}
}
}
if !snapshot.exists() {
self.eventStatus = false
self.tableView.reloadData()
print("No Event here")
} else {
self.eventStatus = true
self.tableView.reloadData()
}
})
}
firebase对象存储在Event类中并存储在字典中。我不认为这个代码是必需的，但这里是更多上下文的事件类代码。
import Foundation
import Firebase
class Event {
var ref: DatabaseReference!
private var _description: String!
private var _imageUrl: String!
private var _eventTitle: String!
private var _eventType: String!
private var _eventTime: String!
private var _eventStartDate: String!
private var _eventEndDate: String!
private var _monthlyRepeat: String!
private var _weeklyRepeat: String!
private var _eventColor: String!
private var _postKey: String!
private var _postRef: DatabaseReference!
var description: String {
return _description
}
var imageUrl: String {
return _imageUrl
}
var eventTitle: String {
return _eventTitle
}
var eventType: String {
return _eventType
}
var eventTime: String {
return _eventTime
}
var eventStartDate: String {
return _eventStartDate
}
var eventEndDate: String {
return _eventEndDate
}
var monthlyRepeat: String {
return _monthlyRepeat
}
var weeklyRepeat: String {
return _weeklyRepeat
}
var eventColor: String {
return _eventColor
}
var postKey: String {
return _postKey
}
init(postKey: String, postData: Dictionary<String, AnyObject>) {
self._postKey = postKey
if let description = postData["description"] as? String {
self._description = description
}
if let imageUrl = postData["event_Image_URL"] as? String {
self._imageUrl = imageUrl
}
if let eventTitle = postData["event_Title"] as? String {
self._eventTitle = eventTitle
}
if let eventType = postData["event_Type"] as? String {
self._eventType = eventType
}
if let eventTime = postData["event_Time"] as? String {
self._eventTime = eventTime
}
if let eventStartDate = postData["start_Date"] as? String {
self._eventStartDate = eventStartDate
}
if let eventEndDate = postData["end_Date"] as? String {
self._eventEndDate = eventEndDate
}
if let monthlyRepeat = postData["monthly_Repeat"] as? String {
self._monthlyRepeat = monthlyRepeat
}
if let weeklyRepeat = postData["weekly_Repeat"] as? String {
self._weeklyRepeat = weeklyRepeat
}
if let eventColor = postData["color"] as? String {
self._eventColor = eventColor
}
let uid = Auth.auth().currentUser?.uid
ref = Database.database().reference()
let eventRef = ref.child("events").child(uid!).child("Monday May, 29")
_postRef = eventRef.child(_postKey)
}
}
答案 0 :(得分：0)
解决此问题的最简单方法是向UILabel添加标题ViewcController，并在快照不可用时更改文字。
或者，如果由于某种原因这对你不起作用，你可以试试这个：
我没有检查过这个，但我可能会让你走上正轨。
首先，您需要更改populateTableView方法，以便即使快照没有结果也会创建events数组。这样，events数组计数将为1（并且一行将添加到tableView），即使快照没有结果。
populateTableView(){
let uid = Auth.auth().currentUser?.uid
ref = Database.database().reference()
ref.child("events").child(uid!).child(currentDate).observeSingleEvent(of: .value, with: { (snapshot) in
self.events = []
if let snapshot = snapshot.children.allObjects as? [DataSnapshot] {
for snap in snapshot {
//print("SNAP: \(snap)")
if let postDict = snap.value as? Dictionary<String, AnyObject> {
let key = snap.key
let event = Event(postKey: key, postData: postDict)
self.events.append(event)
//print(self.events)
}
}
}
else{ // Snapshot does not exist
let postDict: Dictionary<String, AnyObject> // Add an empty Dictionary
let key = -1 // Or what ever value you could not possibly expect
let event = Event(postKey: key, postData: postDict)
self.events.append(event)
self.tableView.reloadData()
print("No Event here")
}
})
}
请注意，当快照无效或可用时，您可以为Dictionary数组添加一个空key个events值。
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return events.count
}
您需要创建两个具有唯一标识符的自定义单元格。
现在你可以＆＃34;实际上＆＃34;填充与此类似的tableView：
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let event = events.[indexPath.row]
let conditionKey = event.key
if(conditionKey == -1){ // or whatever value you gave in populateTableView to indicate that snapshot did not exist
let cell = tableView.dequeueReusableCell(withIdentifier: "identifierCellNotSoGood", for: indexPath) as! CustomCellNotSoGood
cell.noSnapShotLabel1.text = "Sorry, there are no events."
return cell
}
else{
let cell = tableView.dequeueReusableCell(withIdentifier: "identifierCellAllGood", for: indexPath) as! CustomCellAllGood
cell.yourCustomLabel1.text = event.key // Or whatever data you are displaying
cell.sourCustomLabel2.text = event.event // Or whatever data you are displaying
return cell
}
return UITableViewCell
}
如果您需要处理表格单元格的选择，可以执行以下操作：
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
// get rid of the ugly highlighting
tableView.deselectRow(at: indexPath, animated: false)
let event = events.[indexPath.row
let conditionKey = event.key
if(conditionKey == -1){ // or whatever value you gave in populateTableView to indicate that snapshot did not exist
// Do what you need or not
}
else{
// Do something meaningful with your database
doSomething(withEventData: event)
}
}