ios - Swift:如何从我的 TableView 中删除重复项？

Question

这里的问题是我在我的 TableView 中得到了重复项，我知道为什么，但我不知道如何修复它并实现一个不同的系统。

我的应用程序是一个博客阅读器，它使用 PHP 从 MYSQL 数据库读取数据并将 JSON 发送到我的 Swift 应用程序。我的 TableView 有两个部分，一个用于数据库中的所有对象，第二个部分用于当我单击单元格上的关注按钮时，基本上将对象从 mainArray 移动到 followedArray。每个部分都使用一个数组，例如，我将所有对象从 mainArray 移动到 followedArray 并更新表，我在 mainArray 中再次获取所有这些对象，显然是因为 mainarray 是空的，代码只是在做它的工作。

那么我该如何实现一个更好的系统，以便当用户将对象从一个部分移动到另一个部分(或从 mainArray 到 followedArray)时，mainArray 不会重新填充它在 followedArray 中的相同对象。

这是我使用的代码。

MainController.swift - Tableview 所在的类

var mainArray = [Blog]()
var followedArray = [Blog]()

// Title for Header
func tableView(_ tableView: UITableView, titleForHeaderInSection section: Int) -> String? {

    if !(searchController.isActive && searchController.searchBar.text != "") {

        if section == 0 {
            return "Followed Blogs"
        }
        else {
            return "All Blogs"
        }
    }
    return "Filtered Blogs"
}

// Number of Rows in Section
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {

    if !(searchController.isActive && searchController.searchBar.text != "") {

        if section == 0 {

            return followedArray.count
        }
        else if (section == 1) {

            return mainArray.count
        }
    }
    return filteredArray.count
}

// CellForRowAt indexPath
public func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

    let CellIdentifier = "Cell"
    var cell = tableView.dequeueReusableCell(withIdentifier: CellIdentifier) as! CustomCell

    if cell != cell {
        cell = CustomCell(style: UITableViewCellStyle.default, reuseIdentifier: CellIdentifier)
    }

    // Configuring the cell
    var blogObject: Blog

    if !(searchController.isActive && searchController.searchBar.text != "") {
        if indexPath.section == 0 {
            blogObject = followedArray[indexPath.row] 
            cell.populateCell(blogObject, isFollowed: true, indexPath: indexPath, parentView: self)
        }
        else if indexPath.section == 1 {
            blogObject = mainArray[indexPath.row] 
            cell.populateCell(blogObject, isFollowed: false, indexPath: indexPath, parentView: self)
        }
    }
    else {
        blogObject = filteredArray[indexPath.row] 
        cell.populateCell(blogObject, isFollowed: false, indexPath: indexPath, parentView: self)
    }

    return cell
}

// Follow Button
@IBAction func followButtonClick(_ sender: UIButton!) {

    // Adding row to tag
    let buttonPosition = (sender as AnyObject).convert(CGPoint.zero, to: self.myTableView)
    if let indexPath = self.myTableView.indexPathForRow(at: buttonPosition) {

        // Showing Status Labels
        let cell = self.myTableView.cellForRow(at: indexPath) as! CustomCell
        cell.firstStatusLabel.isHidden = false
        cell.secondStatusLabel.isHidden = false

        // Change Follow to Following
        (sender as UIButton).setImage(UIImage(named: "follow.png")!, for: .normal)
        cell.followButton.isHidden = true
        cell.followedButton.isHidden = false

        // Checking wether to import from mainArray or filteredArray to followedArray
        if !(searchController.isActive && searchController.searchBar.text != "") {

            self.myTableView.beginUpdates()

            // ----- Inserting Cell to followedArray -----
            followedArray.insert(mainArray[indexPath.row], at: 0)
            myTableView.insertRows(at: [IndexPath(row: 0, section: 0)], with: .fade)

            // ----- Removing Cell from mainArray -----
            mainArray.remove(at: indexPath.row)
            let rowToRemove = indexPath.row
            self.myTableView.deleteRows(at: [IndexPath(row: rowToRemove, section: 1)], with: .fade)

            self.myTableView.endUpdates()

            myTableView.reloadData()

            // After Updating Table, Save the Archived to UserDefaults
            saveUserDefaults()
        }
        else {

            self.myTableView.beginUpdates()

            // ----- Inserting Cell to followedArray -----
            let blogObject: Blog = filteredArray[indexPath.row]
            let indexOfObjectInArray = mainArray.index(of: blogObject)

            followedArray.insert(blogObject, at: 0)

            // ----- Removing Cell from filteredArray -----
            filteredArray.remove(at: indexPath.row)
            mainArray.remove(at: indexOfObjectInArray!)
            let rowToRemove = indexPath.row
            self.myTableView.deleteRows(at: [IndexPath(row: rowToRemove, section: 0)], with: .fade)

            self.myTableView.endUpdates()

            myTableView.reloadData()

            // After Updating Table, Save the Archived to UserDefaults
            saveUserDefaults()
        }
    }
}


// Retrieving Data from Server
func retrieveDataFromServer() {

    let getDataURL = "http://example.com/receiving.php"
    let url: NSURL = NSURL(string: getDataURL)!

    do {
        let data: Data = try Data(contentsOf: url as URL)
        let jsonArray = try JSONSerialization.jsonObject(with: data, options: .mutableContainers) as! NSMutableArray

        // Looping through jsonArray
        for jsonObject in jsonArray {

            if let blog = Blog.createGame(from: jsonObject as AnyObject) {

                mainArray.append(blog)
            }
        }
    }
    catch {
        print("Error: (Retrieving Data)")
    }
    myTableView.reloadData()
}

Blog.swift - 处理我也使用 NSCoder 的博客对象

import UIKit

class Blog: NSObject, NSCoding {

var blogName: String!
var blogStatus1: String!
var blogStatus2: String!
var blogURL: String!
var blogID: String!
var blogType: String!
var blogDate: String!
var blogPop: String!

static func createBlog(from jsonObject: AnyObject) -> Blog? {

    guard let bID: String = jsonObject.object(forKey: "id") as? String,
        let bName: String = jsonObject.object(forKey: "blogName") as? String,
        let bStatus1: String = jsonObject.object(forKey: "blogStatus1") as? String,
        let bStatus2: String = jsonObject.object(forKey: "blogStatus2") as? String,
        let bURL: String = jsonObject.object(forKey: "blogURL") as? String,
        let bType: String = jsonObject.object(forKey: "blogType") as? String,
        let bDate: String = jsonObject.object(forKey: "blogDate") as? String,
        let bPop: String = jsonObject.object(forKey: "blogPop") as? String

        else {
          print("Error: (Creating Blog Object)")
          return nil
}

let blog = Blog()
    blog.blogName = bName
    blog.blogStatus1 = bStatus1
    blog.blogStatus2 = bStatus2
    blog.blogURL = bURL
    blog.blogID = bID
    blog.blogType = bType
    blog.blogDate = bDate
    blog.blogPop = bPop
    return blog
}

convenience required init?(coder aDecoder: NSCoder) {
    self.init ()
    self.blogName = aDecoder.decodeObject(forKey: "blogName") as! String
    self.blogStatus1 = aDecoder.decodeObject(forKey: "blogStatus1") as! String
    self.blogStatus2 = aDecoder.decodeObject(forKey: "blogStatus2") as! String
    self.blogURL = aDecoder.decodeObject(forKey: "blogURL") as! String
    self.blogID = aDecoder.decodeObject(forKey: "blogID") as! String
    self.blogType = aDecoder.decodeObject(forKey: "blogType") as! String
    self.blogDate = aDecoder.decodeObject(forKey: "blogDate") as! String
    self.blogPop = aDecoder.decodeObject(forKey: "blogPop") as! String
}

func encode(with aCoder: NSCoder) {
    aCoder.encode(blogName, forKey: "blogName")
    aCoder.encode(blogStatus1, forKey: "blogStatus1")
    aCoder.encode(blogStatus2, forKey: "blogStatus2")
    aCoder.encode(blogURL, forKey: "blogURL")
    aCoder.encode(blogID, forKey: "blogID")
    aCoder.encode(blogType, forKey: "blogType")
    aCoder.encode(blogDate, forKey: "blogDate")
    aCoder.encode(blogPop, forKey: "blogPop")
 }
}

在重新填充 mainArray 之前是否有一种方法可以检查 followedArray 中有什么以及丢失或添加到数据库中的任何内容以导入而不创建重复项，因为将添加新博客并且用户将跨部分传输博客所以这是一个我遇到的主要问题。

感谢您的帮助，因为我仍在学习 Swift，谢谢。

Answer 1

我建议将应在后续类别中的博客的唯一标识符保存到一个数组中，并在每次重新加载 tableView 时，将适当的单元格移动到正确的部分。

您似乎在使用 UserDefaults但没有对它们进行修改。使用我的方法，唯一需要保存到 UserDefaults 和从中加载的数组是关注博客的列表。其余的默认为主列表，即使出现新博客也是如此。

你还需要一个数组:

var mainArray = [Blog]()
var followedArray = [Blog]()
var followedIdentifiers = [String]()

或者标识符将属于的任何数据类型

您也可以使用 Set因为您不希望 followedIdentifiers 中有重复项

var followedIdentifiers = Set<String>()

以下是对代码相关部分的修改(我的更改标记为 <---- ):

// Checking whether to import from mainArray or filteredArray to followedArray
if !(searchController.isActive && searchController.searchBar.text != "") {

    self.myTableView.beginUpdates()

    // Save identifier into followedIdentifier array <--------------
    self.followedIdentifiers.insert(mainArray[indexPath.row].blogID)

    // ----- Inserting Cell to followedArray -----
    followedArray.insert(mainArray[indexPath.row], at: 0)
    myTableView.insertRows(at: [IndexPath(row: 0, section: 0)], with: .fade)

    // ----- Removing Cell from mainArray -----
    mainArray.remove(at: indexPath.row)
    let rowToRemove = indexPath.row
    self.myTableView.deleteRows(at: [IndexPath(row: rowToRemove, section: 1)], with: .fade)

    self.myTableView.endUpdates()

    myTableView.reloadData()

    // After Updating Table, Save the Archived to UserDefaults
    saveUserDefaults()
} else {

    self.myTableView.beginUpdates()

    // Remove identifier into followedIdentifier array <------------
    self.followedIdentifiers.remove(followedArray[indexPath.row].blogID)

    // ----- Inserting Cell to followedArray -----
    let blogObject: Blog = filteredArray[indexPath.row]
    let indexOfObjectInArray = mainArray.index(of: blogObject)

    followedArray.insert(blogObject, at: 0)

    // ----- Removing Cell from filteredArray -----
    filteredArray.remove(at: indexPath.row)
    mainArray.remove(at: indexOfObjectInArray!)
    let rowToRemove = indexPath.row
    self.myTableView.deleteRows(at: [IndexPath(row: rowToRemove, section: 0)], with: .fade)

    self.myTableView.endUpdates()

    myTableView.reloadData()

    // After Updating Table, Save the Archived to UserDefaults
    saveUserDefaults()
}

// Retrieving Data from Server
func retrieveDataFromServer() {

    let getDataURL = "http://example.com/receiving.php"
    let url: NSURL = NSURL(string: getDataURL)!

    do {
        let data: Data = try Data(contentsOf: url as URL)
        let jsonArray = try JSONSerialization.jsonObject(with: data, options: .mutableContainers) as! NSMutableArray

        // Clear the arrays      <-------------
        self.followedArray = [Blog]()
        self.mainArray = [Blog()]

        // Looping through jsonArray
        for jsonObject in jsonArray {

            if let blog = Blog.createBlog(from: jsonObject as AnyObject) {
                // Check if identifiers match <------------
                if followedIdentifiers.contains(blog.blogID) {
                    self.followedArray.append(blog)
                } else {
                    self.mainArray.append(blog)
                }

            }
        }
    } catch {
        print("Error: (Retrieving Data)")
    }
    myTableView.reloadData()
}

为了让它跨 session 工作，你必须在你的saveUserDefaults()中有类似的东西

UserDefaults.standard.setValue(Array(self.followedIdentifiers), forKey: "someName")

这是你从 UserDefaults 加载的地方

self.followedIdentifiers = Set(UserDefaults.standard.stringArray(forKey: "someName"))