我使用Firebase值创建了一些简单的计算系统。但是，如果我对它进行评级，计算和值都可以，但它不会更新标签。
这就是我获取价值并进行计算的方式：
let ref = FIRDatabase.database().reference().child("Snuses").queryOrdered(byChild: "Brand")
.queryEqual(toValue: brandName)
ref.observeSingleEvent(of: .value, with: { (snapshot) in
if snapshot.exists(){
let enumerator = snapshot.children
while let thisProduct = enumerator.nextObject() as? FIRDataSnapshot {
// Chances are you'd have to create a dictionary
let thisProductDict = thisProduct.value as! [String:AnyObject]
let rating = thisProductDict["rating"] as! Double
let ratersCount = thisProductDict["ratersCount"] as! Double
let ratingToShow: String = String((ratersCount == 0) ? 0 : rating / ratersCount)
let productObject = Product(
rating: rating,
ratersCount: ratersCount,
ratingToShow: ratingToShow)
self.products.append(productObject)
}
self.tableView.reloadData()
在cellForRowAtIndexPath中，我尝试在标签上显示ratingToShow：
cell.ratingLabel.text = products[indexPath.row].ratingToShow
我添加值的方式如下：
let ratingToShow: String = String((products[indexPath.row].ratersCount == 0) ? 0 : products[indexPath.row].rating / products[indexPath.row].ratersCount)
cell.likeLabel.text = ratingToShow
self.databaseRef.child("productRatings").child(self.currentUser.generalDetails.uid).child(self.products[indexPath.row].snusProductTitle).child(self.currentUser.generalDetails.uid).observeSingleEvent(of: .value, with: { (snapshot) in
if snapshot.value as? Bool == true{
self.databaseRef.child("productRatings").child(self.currentUser.generalDetails.uid).child(self.products[indexPath.row].snusProductTitle).child("rating").observeSingleEvent(of: .value, with: { (snapshot) in
let currentUserRate = snapshot.value
cell.ratingView.rating = currentUserRate as! Double
})
}else{
cell.ratingView.rating = 0.0
}
cell.ratingView.didFinishTouchingCosmos = { rating in
if snapshot.value as? Bool == true{
self.databaseRef.child("productRatings").child(self.currentUser.generalDetails.uid).child(self.products[indexPath.row].snusProductTitle).child("rating").observeSingleEvent(of: .value, with: { (snapshot) in
let currentUserRate = snapshot.value as? Double
self.databaseRef.child("Snuses").child(self.products[indexPath.row].snusProductTitle).child("rating").runTransactionBlock({
(currentData:FIRMutableData!) in
var value = currentData.value as? Double
if (value == nil) {
value = 0.0
}
currentData.value = value! - currentUserRate!
cell.update(rating)
return FIRTransactionResult.success(withValue: currentData)
})
self.databaseRef.child("Snuses").child(self.products[indexPath.row].snusProductTitle).child("rating").runTransactionBlock({
(currentData:FIRMutableData!) in
var value = currentData.value as? Double
if (value == nil) {
value = 0.0
}
currentData.value = value! + rating
cell.update(rating)
return FIRTransactionResult.success(withValue: currentData)
})
self.databaseRef.child("productRatings").child(self.currentUser.generalDetails.uid).child(self.products[indexPath.row].snusProductTitle).runTransactionBlock({
(currentData:FIRMutableData!) in
var value = currentData.value as? Bool
if (value == nil) {
value = true
}
currentData.value = [self.currentUser.generalDetails.uid:true]
self.databaseRef.child("productRatings").child(self.currentUser.generalDetails.uid).child(self.products[indexPath.row].snusProductTitle).updateChildValues(["rating": rating])
return FIRTransactionResult.success(withValue: currentData)
})
})
}else{
self.databaseRef.child("Snuses").child(self.products[indexPath.row].snusProductTitle).child("ratersCount").runTransactionBlock({
(currentData:FIRMutableData!) in
var value = currentData.value as? Double
if (value == nil) {
value = 0.0
}
currentData.value = value! + 1
return FIRTransactionResult.success(withValue: currentData)
})
self.databaseRef.child("Snuses").child(self.products[indexPath.row].snusProductTitle).child("rating").runTransactionBlock({
(currentData:FIRMutableData!) in
var value = currentData.value as? Double
if (value == nil) {
value = 0.0
}
currentData.value = value! + rating
cell.update(rating)
return FIRTransactionResult.success(withValue: currentData)
})
self.databaseRef.child("productRatings").child(self.currentUser.generalDetails.uid).child(self.products[indexPath.row].snusProductTitle).runTransactionBlock({
(currentData:FIRMutableData!) in
var value = currentData.value as? Bool
if (value == nil) {
value = true
}
currentData.value = [self.currentUser.generalDetails.uid:true]
self.databaseRef.child("productRatings").child(self.currentUser.generalDetails.uid).child(self.products[indexPath.row].snusProductTitle).updateChildValues(["rating": rating])
return FIRTransactionResult.success(withValue: currentData)
})
}
}
})
我应该采取哪些不同的方式？
答案 0 :(得分：0)
要轻松操作用户界面中的增量值，一般和最基本的方法是这样的： -
更新Firebase数据库中的帖子：使用 runTransactionBlock
然后将您当前的dataSource更新为Product结构中检索和存储的数据中的相同值。
例如： - 一旦您的用户点击喜欢按钮或喜欢它，您就会在后端（Firebase）和products[indexPath.row].ratingToShow中更新相应操作的值，然后调用 self.tableView.reloadData 即可。这样，每次用户喜欢或不喜欢保存带宽的帖子时，您都不必从数据库中获取当前没有喜欢的内容。
如果你的喜欢按钮在TableViewCell类中有 @IBAction ，那么只需对 yourTableViewController 进行控制器引用并更改数据源： -
class yourTabelViewCell : UITableViewCell{
var tableController : yourTableViewcontroller!
var indexPathForCell : Int!
@IBAction func likeBtnAction(_ sender: UIButton) {
//User likes or dislikes the post....
self.tableController.products[self.indexPathForCell]. ratingToShow = //Manipulate the value +1 or -1
self.tableController.yourTableView.reloadData() // Given yourTableView is the custom tableView you have implemented in your viewController
}
}
要获取 indexPathForCell ，只需初始化 cellForRowAt indexPath : _
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "yourTabelViewCell_identifier", for: indexPath) as! yourTabelViewCell
cell.likeLabel.text = products[indexPath.row].ratingToShow
cell.indexPathForCell = indexPath.row
return cell
}
不要担心用户在喜欢或不喜欢帖子时丢失网络连接， runTransactionBlock 会加载到本地缓存中，因此一旦您的用户重新获得网络连接，那些命令将被执行