Swift：如何从表视图中删除重复项？

Question

这里的问题是我在表格视图中得到了重复项，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，以将JSON发送到我的Swift应用程序。我的表视图有两个部分，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跟随按钮时，基本上将对象从mainArray移动到followArray。每个部分都使用一个数组，例如我将所有对象从mainArray移动到followArray，然后我更新表，我在mainArray中再次获取所有这些对象，显然因为mainarray是空的，代码正在完成它的工作。

那么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移动到followArray）时，mainArray不会重新填充它拥有的相同对象，并且现在位于FollowArray中

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 - 处理我用户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")
 }
}

有没有办法在重新填充mainArray之前检查以查看followArray中的内容以及丢失或添加到数据库中的任何内容以进行导入而不创建重复项，因为将添加新博客并且用户将跨部门传输博客以便这是一个我遇到的主要问题。

感谢帮助，因为我还在学习Swift，谢谢。

Answer 1

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

您似乎正在使用UserDefaults，但没有对它们进行任何修改。使用我的方法，需要保存到UserDefaults并从UserDefaults加载的唯一数组是跟随的博客列表。其余的默认为主列表，即使新博客出现。

你还需要一个阵列：

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

或标识符将在

中的任何数据类型

你也可以使用Set，因为你想在followIdentifiers中没有重复

var followedIdentifiers = Set<String>()

以下是对代码相关部分的修改（我的更改标有<----）：

// 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()
}

为了使其能够跨会话，您必须在saveUserDefaults()

中使用与此相似的内容

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

这是从UserDefaults

加载的地方

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