Swift 冗余一致性

Posted 2023-02-23

【中文标题】Swift 冗余一致性

【英文标题】：Swift Redundant conformance

【发布时间】：2016-07-17 10:47:42

【问题描述】：

我正在学习 ios。现在是 iOS 上的本地数据库。我来自 android，发现本地数据库有点难以理解。我写了一个问题让我投了几票（而不是简单地使用CoreStore 或Sync 或MagicalRecord）。然后我开始阅读this tutorial。下载示例项目后，我在BeerListViewController 中收到Redundant conformance of 'BeerListViewController' to protocol 'UITableViewDataSource' 错误。请告诉我如何解决它。

代码如下：

import UIKit
import Foundation

class BeerListViewController: UITableViewController 

  @IBOutlet weak var sortByControl: UISegmentedControl!
  @IBOutlet weak var searchBar: UISearchBar!

  let sortKeyName   = "name"
  let sortKeyRating = "beerDetails.rating"
  let wbSortKey     = "wbSortKey"

  //------------------------------------------
  // Rating

  var amRatingCtl: AnyObject!

  let beerEmptyImage: UIImage = UIImage(named: "beermug-empty")!
  let beerFullImage:  UIImage = UIImage(named: "beermug-full")!

  //#####################################################################
  // MARK: - Initialization

  required init(coder aDecoder: NSCoder) 
    // Automatically invoked by UIKit as it loads the view controller from the storyboard.

    amRatingCtl = AMRatingControl(location: CGPointMake(190, 10),
                                emptyImage: beerEmptyImage,
                                solidImage: beerFullImage,
                              andMaxRating: 5)    

    // A call to super is required after all variables and constants have been assigned values but before anything else is done.
    super.init(coder: aDecoder)!
  
  //#####################################################################
  // MARK: - Segues

  override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) 
    // Allows data to be passed to the new view controller before the new view is displayed.

    // "destinationViewController" must be cast from its generic type (AnyObject) to the specific type used in this app
    // (BeerDetailViewController) before any of its properties can be accessed.
    let controller = segue.destinationViewController as? BeerDetailViewController

    if segue.identifier == "editBeer" 

      controller!.navigationItem.rightBarButtonItems = []

    //------------------------------------------------------------------------------------
     else if segue.identifier == "addBeer" 

      controller!.navigationItem.leftBarButtonItem  = UIBarButtonItem(title: "Cancel",
                                                                      style: UIBarButtonItemStyle.Plain,
                                                                     target: controller,
                                                                     action: "cancelAdd")

      controller!.navigationItem.rightBarButtonItem = UIBarButtonItem(title: "Done",
                                                                      style: UIBarButtonItemStyle.Done,
                                                                     target: controller,
                                                                     action: "addNewBeer")
    
  
  //#####################################################################
  // MARK: - UIViewController - Responding to View Events

  override func viewWillAppear(animated: Bool) 

    super.viewWillAppear(animated)

    //------------------------------------------
    // Sorting Key

    if !(NSUserDefaults.standardUserDefaults().objectForKey(wbSortKey) != nil) 
      // User's sort preference has not been saved.  Set default to sort by rating.
      NSUserDefaults.standardUserDefaults().setObject(sortKeyRating, forKey: wbSortKey)
    

    // Keep the sort control in the UI in sync with the means by which the list is sorted.
    if NSUserDefaults.standardUserDefaults().objectForKey(wbSortKey) as! String == sortKeyName 
      sortByControl.selectedSegmentIndex = 1
    
    //------------------------------------------
    fetchAllBeers()

    // Cause tableView(cellForRowAtIndexPath) to be called again for every visible row in order to update the table.
    tableView.reloadData()
  
  //#####################################################################
  // MARK: - UIViewController - Managing the View

  // viewDidLoad() is called after prepareForSegue().

  override func viewDidLoad() 

    super.viewDidLoad()

    //------------------------------------------

    tableView.contentOffset = CGPointMake(0, 44)
  
  //#####################################################################
  // MARK: - Action Methods

  @IBAction func sortByControlChanged(sender: UISegmentedControl) 

    switch sender.selectedSegmentIndex 

    case 0:
      NSUserDefaults.standardUserDefaults().setObject(sortKeyRating, forKey: wbSortKey)
      fetchAllBeers()
      tableView.reloadData()

    case 1:
      NSUserDefaults.standardUserDefaults().setObject(sortKeyName, forKey: wbSortKey)
      fetchAllBeers()
      tableView.reloadData()

    default:
      break
    
  
  //#####################################################################
  // MARK: - MagicalRecord Methods

  func fetchAllBeers() 
  
  //#####################################################################

  func saveContext() 
  
  //#####################################################################


//#####################################################################
// MARK: - Table View Data Source

extension BeerListViewController: UITableViewDataSource  // THE ERROR APPEARS HERE

  //#####################################################################
  // MARK: Configuring a Table View

  override func numberOfSectionsInTableView(tableView: UITableView) -> Int 
    return 1
  
  //#####################################################################

  override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int 
    return 10
  
  //#####################################################################

  override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell 

    let cellIdentifier = "Cell"
    let cell = tableView.dequeueReusableCellWithIdentifier(cellIdentifier)

    configureCell(cell!, atIndex: indexPath)

    return cell!
  
  //#####################################################################
  // MARK: Helper Methods

  func configureCell(cell: UITableViewCell, atIndex indexPath: NSIndexPath) 

    //------------------------------------------
    // Rating

    let ratingText = ""

    let myRect = CGRect(x:250, y:0, width:200, height:50)
    var ratingLabel = UILabel(frame: myRect)

    if !(cell.viewWithTag(20) != nil) 

      ratingLabel.tag = 20
      ratingLabel.text = ratingText
      cell.addSubview(ratingLabel)

     else 
      ratingLabel = cell.viewWithTag(20) as! UILabel
    
    //----------------------
    ratingLabel.text = ratingText

  
  //#####################################################################
  // MARK: Inserting or Deleting Table Rows

  override func tableView(tableView: UITableView, canEditRowAtIndexPath indexPath: NSIndexPath) -> Bool 
    return true
  
  //#####################################################################

  override func tableView(tableView: UITableView, commitEditingStyle editingStyle: UITableViewCellEditingStyle, forRowAtIndexPath indexPath: NSIndexPath) 

    // When the commitEditingStyle method is present in a view controller, the table view will automatically enable swipe-to-delete.

    if (editingStyle == .Delete) 

    
  
  //#####################################################################

//#####################################################################
// MARK: - Search Bar Delegate

extension BeerListViewController: UISearchBarDelegate 

  // MARK: Editing Text

  func searchBar(searchBar: UISearchBar, textDidChange searchText: String) 

    if searchBar.text != "" 
      performSearch()

     else 
      fetchAllBeers()
      tableView.reloadData()
    
  
  //#####################################################################

  func searchBarTextDidBeginEditing(searchBar: UISearchBar) 
    searchBar.showsCancelButton = true
  
  //#####################################################################
  // MARK: Clicking Buttons

  func searchBarCancelButtonClicked(searchBar: UISearchBar) 

    searchBar.resignFirstResponder()
    searchBar.text = ""
    searchBar.showsCancelButton = false
    fetchAllBeers()
    tableView.reloadData()
  
  //#####################################################################

  func searchBarSearchButtonClicked(searchBar: UISearchBar) 
    // This method is invoked when the user taps the Search button on the keyboard.

    searchBar.resignFirstResponder()
    performSearch()
  
  //#####################################################################
  // MARK: Helper Methods

  func performSearch() 
    tableView.reloadData()
  
  //#####################################################################
  // MARK: - Bar Positioning Delegate
  //         UISearchBarDelegate Protocol extends UIBarPositioningDelegate protocol.
  //         Method positionForBar is part of the UIBarPositioningDelegate protocol.

  // This delegate method is required to prevent a gap between the top of the screen and the search bar.
  // That happens because, as of iOS 7, the status bar is no longer a separate area but is directly drawn on top of the view controller.

  func positionForBar(bar: UIBarPositioning) -> UIBarPosition 
    // Tell the search bar to extend under the status bar area.

    return .TopAttached
  
  //#####################################################################

【问题讨论】：

你能显示你的类定义吗？ BeerListViewController?

可能是***.com/questions/30867937/…的副本。

@Paulw11，添加代码，请看

【参考方案1】：

UITableViewController 按照定义符合UITableViewDataSource。

只需删除协议一致性

extension BeerListViewController  ...