У меня есть три разных типа ячеек в tableViewController. Я получаю тип ячейки и objectId элемента из другого класса. Затем я перехожу к каждой ячейке в методе cellForRowAt и загружаю все данные. Этот метод привел меня к двум проблемам: 1) динамическая высота одной из ячеек не работает, потому что текст ее метки не найден до тех пор, пока ячейка не будет создана. 2) Все ячейки имеют «дерганый» вид (я вижу, что строки заполняются при прокрутке вниз, я думаю, потому что он загружает содержимое при каждой прокрутке), когда я прокручиваю таблицу вниз.
Поэтому я хочу предварительно загрузить все данные и поместить их в cellForRowAt вместо поиска данных в cellForRowAt. Это решит обе проблемы, но я понятия не имею, как это сделать. Основываясь на своих знаниях в области кодирования, я бы поместил информацию, которая будет находиться в каждой ячейке в массивах, а затем соответствующим образом заполнил ячейки, но я не знаю, как это сделать при использовании 3 разных ячеек, потому что для помещения информации в ячейки из массива я нужно будет использовать indexPath.row; что я не могу сделать, потому что я загружаю 3 разных типа данных и добавляю их в разные массивы, поэтому indexPaths не будут правильно выровнены. Это единственный способ, которым я могу думать об этом, и это неправильно. Как решить эту проблему?
Я скопировал свой код внизу, чтобы вы могли видеть, как я сейчас загружаю ячейки, и, возможно, вы сможете понять, как исправить мою проблему:
func loadNews() {
//start finding followers
let followQuery = PFQuery(className: "Follow")
followQuery.whereKey("follower", equalTo: PFUser.current()?.objectId! ?? String())
followQuery.findObjectsInBackground { (objects, error) in
if error == nil {
//clean followArray
self.followArray.removeAll(keepingCapacity: false)
//find users we are following
for object in objects!{
self.followArray.append(object.object(forKey: "following") as! String)
}
self.followArray.append(PFUser.current()?.objectId! ?? String()) //so we can see our own post
//getting related news post
let newsQuery = PFQuery(className: "News")
newsQuery.whereKey("user", containedIn: self.followArray) //find this info from who we're following
newsQuery.limit = 30
newsQuery.addDescendingOrder("createdAt") //get most recent
newsQuery.findObjectsInBackground(block: { (objects, error) in
if error == nil {
//clean up
self.newsTypeArray.removeAll(keepingCapacity: false)
self.objectIdArray.removeAll(keepingCapacity: false)
self.newsDateArray.removeAll(keepingCapacity: false)
for object in objects! {
self.newsTypeArray.append(object.value(forKey: "type") as! String) //get what type (animal / human / elements)
self.objectIdArray.append(object.value(forKey: "id") as! String) //get the object ID that corresponds to different class with its info
self.newsDateArray.append(object.createdAt) //get when posted
}
self.tableView.reloadData()
} else {
print(error?.localizedDescription ?? String())
}
})
} else {
print(error?.localizedDescription ?? String())
}
}
}
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let type = newsTypeArray[indexPath.row]
if type == "element" {
let cell = tableView.dequeueReusableCell(withIdentifier: "ElementCell") as! ElementCell
let query = query(className: "Element")
query.whereKey("objectId", equalTo: self.objectIdArray[indexPath.row])
query.limit = 1
query.findObjectsInBackground(block: { (objects, error) in
if error == nil {
for object in objects! {
let name = (object.object(forKey: "type") as! String)
let caption = (object.object(forKey: "caption") as! String) //small description (usually 2 lines)
cell.captionLabel.text = caption
}
} else {
print(error?.localizedDescription ?? String())
}
})
return cell
} else if type == "human" {
let cell = tableView.dequeueReusableCell(withIdentifier: "HumanCell") as! HumanCell
let query = query(className: "Human")
query.whereKey("objectId", equalTo: self.objectIdArray[indexPath.row])
query.limit = 1
query.findObjectsInBackground(block: { (objects, error) in
if error == nil {
for object in objects! {
let name = (object.object(forKey: "name") as! String)
let caption = (object.object(forKey: "caption") as! String) //small description (1 line)
cell.captionLabel.text = caption
}
} else {
print(error?.localizedDescription ?? String())
}
})
return cell
} else { //its an animal cell
let cell = tableView.dequeueReusableCell(withIdentifier: "Cell") as! AnimalCell
let query = query(className: "Animals")
query.whereKey("objectId", equalTo: self.objectIdArray[indexPath.row])
query.limit = 1
query.findObjectsInBackground(block: { (objects, error) in
if error == nil {
for object in objects! {
let caption = (object.object(forKey: "caption") as! String) //large description of animal (can be 2 - 8 lines)
cell.captionLabel.text = caption
}
} else {
print(error?.localizedDescription ?? String())
}
})
return cell
}
}
----- Редактировать ------
Реализация логики @Woof:
В отдельном файле Swift:
class QueryObject {
var id: String?
var date: Date?
var userID : String?
var name: String?
}
class Element: QueryObject {
var objectID : String?
var owner : String?
var type : String?
var ability : String?
var strength : String?
}
class Human: QueryObject {
var objectID : String?
var follower : String?
var leader : String?
}
class Animal: QueryObject {
var objectID : String?
var type: String?
var owner : String?
var strength : String?
var speed : String?
var durability : String?
}
В TableviewController:
var tableObjects: [QueryObject] = []
func loadNews() {
//start finding followers
let followQuery = PFQuery(className: "Follow")
followQuery.whereKey("follower", equalTo: PFUser.current()?.objectId! ?? String())
followQuery.findObjectsInBackground { [weak self](objects, error) in
if error == nil {
//clean followArray
self?.followArray.removeAll(keepingCapacity: false)
//find users we are following
for object in objects!{
self?.followArray.append(object.object(forKey: "following") as! String)
}
self?.followArray.append(PFUser.current()?.objectId! ?? String()) //so we can see our own post
//this is a custom additional method to make a query
self?.queryNews(name: "News", followArray: self?.followArray ?? [], completionHandler: { (results) in
//if this block is called in a background queue, then we need to return to the main one before making an update
DispatchQueue.main.async {
//check that array is not nil
if let objects = results {
self?.tableObjects = objects
self?.tableView.reloadData()
}else{
//objects are nil
//do nothing or any additional stuff
}
}
})
} else {
print(error?.localizedDescription ?? String())
}
}
}
//I've made the code separated, to make it easy to read
private func queryNews(name: String, followArray: [String], completionHandler: @escaping (_ results: [QueryObject]?) -> Void) {
//making temp array
var temporaryArray: [QueryObject] = []
//getting related news post
let newsQuery = PFQuery(className: "News")
newsQuery.whereKey("user", containedIn: followArray) //find this info from who we're following
newsQuery.limit = 30
newsQuery.addDescendingOrder("createdAt") //get most recent
newsQuery.findObjectsInBackground(block: { [weak self] (objects, error) in
if error == nil {
//now the important thing
//we need to create a dispatch group to make it possible to load all additional data before updating the table
//NOTE! if your data are large, maybe you need to show some kind of activity indicator, otherwise user won't understand what is going on with the table
let dispathGroup = DispatchGroup()
for object in objects! {
//detecting the type of the object
guard let type = object.value(forKey: "type") as? String else{
//wrong value or type, so don't check other fields of that object and start to check the next one
continue
}
let userID = object.value(forKey: "user") as? String
let id = object.value(forKey: "id") as? String
let date = object.createdAt
//so now we can check the type and create objects
//and we are entering to our group now
dispathGroup.enter()
switch type {
case "element":
//now we will make a query for that type
self?.queryElementClass(name: "element", id: id!, completionHandler: { (name, objectID, owner, type, ability, strength) in
//I've added a check for those parameters, and if they are nil, I won't add that objects to the table
//but you can change it as you wish
if let objectName = name, let objectsID = objectID {
//now we can create an object
let newElement = Element()
newElement.userID = userID
newElement.id = id
newElement.date = date
newElement.objectID = objectID
newElement.owner = owner
newElement.type = type
newElement.ability = ability
newElement.strength = strength
temporaryArray.append(newElement)
}
//don't forget to leave the dispatchgroup
dispathGroup.leave()
})
case "human":
//same for Human
self?.queryHumanClass(name: "human", id: id!, completionHandler: { (name, objectID, follower, leader) in
if let objectName = name, let objectsID = objectID {
let newHuman = Human()
newHuman.userID = userID
newHuman.id = id
newHuman.date = date
temporaryArray.append(newHuman)
}
//don't forget to leave the dispatchgroup
dispathGroup.leave()
})
case "animal":
//same for animal
self?.queryAnimalClass(name: "animal", id: id!, completionHandler: { (name, objectID, type, owner, strength, speed, durability) in
if let objectName = name, let objectCaption = caption {
let newAnimal = Animal()
newAnimal.userID = userID
newAnimal.id = id
newAnimal.date = date
temporaryArray.append(newAnimal)
}
//don't forget to leave the dispatchgroup
dispathGroup.leave()
})
default:
//unrecognized type
//don't forget to leave the dispatchgroup
dispathGroup.leave()
}
}
//we need to wait for all tasks entered the group
//you can also add a timeout here, like: user should wait for 5 seconds maximum, if all queries in group will not finished somehow
dispathGroup.wait()
//so we finished all queries, and we can return finished array
completionHandler(temporaryArray)
} else {
print(error?.localizedDescription ?? String())
//we got an error, so we will return nil
completionHandler(nil)
}
})
}
//the method for making query of an additional class
private func queryElementClass(name: String, id: String, completionHandler: @escaping (_ name: String?, _ objectID: String?, _ owner: String?, _ type: String?, _ ability: String?, _ strength: String?) -> Void) {
let query = PFQuery(className: "Elements")
query.whereKey("objectId", equalTo: id)
query.limit = 1
query.findObjectsInBackground { (objects, error) in
if error == nil {
if let object = objects?.first {
let name = object.object(forKey: "type") as? String
let objectID = object.object(forKey: "objectID") as? String
let owner = object.object(forKey: "owner") as? String
let type = object.object(forKey: "type") as? String
let ability = object.object(forKey: "ability") as? String
let strength = object.object(forKey: "strength") as? String
completionHandler(name, objectID, owner, type, ability, strength)
} else {
print(error?.localizedDescription ?? String())
completionHandler(nil, nil, nil, nil, nil, nil)
}
} else {
print(error?.localizedDescription ?? String())
}
}
}
//the method for making query of an additional class
private func queryHumanClass(name: String, id: String, completionHandler: @escaping (_ name: String?, _ objectID: String?, _ follower: String?, _ leader: String?) -> Void) {
let query = PFQuery(className: "Human")
query.whereKey("objectId", equalTo: id)
query.limit = 1
query.findObjectsInBackground(block: { (objects, error) in
if let object = objects?.first {
let name = object.object(forKey: "type") as? String
let objectID = object.object(forKey: "objectID") as? String
let follower = object.object(forKey: "follower") as? String
let leader = object.object(forKey: "leader") as? String
completionHandler(name, objectID, follower, leader)
} else {
print(error?.localizedDescription ?? String())
completionHandler(nil, nil, nil, nil)
}
})
}
//the method for making query of an additional class
private func queryAnimalClass(name: String, id: String, completionHandler: @escaping (_ name: String?, _ objectID: String?, _ owner: String?, _ type: String?, _ strength: String?, _ speed: String?, _ durability: String?) -> Void) {
let query = PFQuery(className: "Animals")
query.whereKey("objectId", equalTo: id)
query.limit = 1
query.findObjectsInBackground(block: { (objects, error) in
if let object = objects?.first {
let name = object.object(forKey: "type") as? String
let objectID = object.object(forKey: "objectID") as? String
let owner = object.object(forKey: "owner") as? String
let strength = object.object(forKey: "strength") as? String
let type = object.object(forKey: "type") as? String
let speed = object.object(forKey: "speed") as? String
let durability = object.object(forKey: "durability") as? String
completionHandler(name, objectID, owner, type, strength, speed, durability)
} else {
print(error?.localizedDescription ?? String())
completionHandler(nil, nil, nil, nil, nil, nil, nil)
}
})
}
