更改后如何更新表格视图单元格

Question

当我上下滚动时，tableview 单元格设置了超时，因此会影响滞后。

我只想在数据更新时更新。

Post.swift（它是模型）

import Foundation
import Parse

class Post: PFObject, PFSubclassing {

    @NSManaged var postBy: PFUser?

    @NSManaged var postUser: String?
    @NSManaged var postUserImg: PFFile?



    @NSManaged var postText: String?
    @NSManaged var postImg: PFFile?
    @NSManaged var sell: NSNumber?

    @NSManaged var commentPointer: PFObject?
    @NSManaged var commentBy: String?
    @NSManaged var comment: String?

    @NSManaged var liked: NSArray?
    @NSManaged var likeCount: NSNumber?

    @NSManaged var mention: NSArray?
    @NSManaged var hashtag: NSArray?


    static func parseClassName() -> String {
        return "Post"
    }



    override class func query() -> PFQuery<PFObject>? {

        let query = PFQuery(className: Post.parseClassName())


        return query
    }

}

extension Post: FeedCellSupport {


    var username:String?{


        return postUser
    }

    var userImg:PFFile?{



        return postUserImg
    }

    var commentText:String?{

        guard let commentTxt = comment else {
            return ""
        }


        return commentTxt


    }

TableView.swift

protocol FeedCellSupport {
    var postDate: String? { get }
    var postId: String? { get }
    var postObj: PFObject? { get }
    var img: PFFile? { get }
    var username:String?{ get }
    var userImg:PFFile?{ get }

    var commentText:String?{ get }
    var commentFrom:String?{ get }

    var postText: String? { get }
    var likes: Int? { get }
    var isLiked: Bool? { get }
    var isSell: Bool? { get }

    var hashtags: NSArray? { get }
    var mentions: NSArray? { get }

}


func fetchObjects() {

        let postQuery = Post.query()?
                        .whereKeyExists("objectId")
                        .includeKeys(["postBy", "commentPointer", "commentPointer.commentBy", "commentBy"])
                        .order(byDescending: "createdAt")
                        as! PFQuery<Post>

        postQuery.limit = self.page
        postQuery.cachePolicy = .networkElseCache

        postQuery.findObjectsInBackground { (object:[Post]?, error:Error?) in

            if error == nil {

                self.results = object!

            }else {
                print(error?.localizedDescription as Any)
            }

            self.tableView.reloadData()
            self.refresher.endRefreshing()
        }


    }


 override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

        let cell = tableView.dequeueReusableCell(withIdentifier: "ShopDetailCell", for: indexPath) as! ShopDetailCell

        if let object = results[indexPath.row] as? FeedCellSupport{




            cell.postID = object.postObj!
            cell.userNameLabel.text = object.username!
            cell.userNameLabel.sizeToFit()

            cell.descriptionLabel.text = object.postText!
            cell.descriptionLabel.sizeToFit()

            cell.commentByLabel.text = object.commentFrom!
            cell.commentByLabel.sizeToFit()

            cell.commentLabel.text = object.commentText!
            cell.commentLabel.sizeToFit()
 cell.delegate = self

        }
        return cell
    }

如何确保数据仅在数据发生变化时才更新？

Answer 1

您的应用程序有哪些功能？您的问题与适合完成任务的方式有关，即：更新应用内容。

所以它是关于业务逻辑的：什么时候应该更新信息？

您的问题的解决方案是使用用户切换事件来刷新内容或其他可能的解决方案，例如 Application Delegate。

除了这些答案，内容无法按照您的期望自动更新tableview。

更新

我认为这行代码是滞后的：

if let object = results[indexPath.row] as? FeedCellSupport{
    //other code
}

因为这些大括号内的代码正在处理数据设置。您可以尝试模拟本地数据而不是这个 results 数组来说明这是否是问题所在。