Question

我正在制作鸡尾酒iOS应用程序。

我正在为tableview添加字符串（＆＃34; cabinet＆＃34;的一个成分）。用户输入成分然后按下按钮ADD。它成功地将其添加到核心数据，但它不会立即出现。我做错了什么？

以下是我的代码，谢谢！

的ViewController：

import UIKit
import CoreData

class CabinetViewController: UIViewController, UITextFieldDelegate, UITableViewDataSource, UITableViewDelegate {

    var ingredientArray = [String]()
    var display = [String]()
    var dbIngredients = [String]()

    let ingredientFetch = NSFetchRequest(entityName: "Cabinet")
    var fetchedIngredient = [Cabinet]()

    @IBOutlet weak var TextUI: UITextField!
    @IBOutlet weak var Button: UIButton!
    @IBOutlet weak var TableView: UITableView!

    let moc = DataController().managedObjectContext

    override func viewDidLoad() {
        super.viewDidLoad()

        TextUI.delegate = self
        TextUI.addTarget(self, action: "textFieldDidChange:", forControlEvents: UIControlEvents.EditingChanged)

        TableView.delegate = self
        TableView.dataSource = self
        TableView.registerClass(UITableViewCell.self,
            forCellReuseIdentifier: "Cell")

        // fetch Core Data
        do{
            fetchedIngredient = try moc.executeFetchRequest(ingredientFetch) as! [Cabinet]
        } catch {
            fatalError()
        }

        let postEndpoint: String = "http://www.thecocktaildb.com/api/json/v1/1/list.php?i=list"

        guard let url = NSURL(string: postEndpoint) else {
            print("Error: cannot create URL")
            return
        }

        let urlRequest = NSURLRequest(URL: url)
        let config = NSURLSessionConfiguration.defaultSessionConfiguration()
        let session = NSURLSession(configuration: config)

        let task = session.dataTaskWithRequest(urlRequest, completionHandler: { (data, response, error) in
            guard let responseData = data else {
                print("Error: did not receive data")
                return
            }
            guard error == nil else {
                print("error calling GET on www.thecocktaildb.com")
                print(error)
                return
            }

            let post: NSDictionary
            do {
                post = try NSJSONSerialization.JSONObjectWithData(responseData,
                    options: []) as! NSDictionary
            } catch  {
                print("error trying to convert data to JSON")
                return
            }

            var count = 1
            if let drinks = post["drinks"] as? [NSDictionary] {
                for drink in drinks {
                    if let strIngredient = drink["strIngredient1"] as? String {
                        print(String(count) + ". " + strIngredient)
                        self.dbIngredients.append(strIngredient)
                        count++
                    }
                }
            }
        })
        task.resume()
        TableView.reloadData()
    }

    func textFieldDidChange(textField: UITextField) {
        search(self.TextUI.text!)
    }

    func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
        Button.addTarget(self, action: "buttonPressed:", forControlEvents: .TouchUpInside)
        return true
    }

    func buttonPressed(sender: UIButton!) {
        //ingredientArray.append(TextUI.text!)

        let entity = NSEntityDescription.insertNewObjectForEntityForName("Cabinet", inManagedObjectContext: moc) as! Cabinet
        entity.setValue(TextUI.text!, forKey: "ingredient")
        do{
            try moc.save()
        }catch {
            fatalError("failure to save context: \(error)")
        }
        showAlertButtonTapped(Button)
//        dispatch_async(dispatch_get_main_queue(), { () -> Void in
//            self.TableView.reloadData()
//        })
    }

    @IBAction func showAlertButtonTapped(sender: UIButton) {
        // create the alert
        let alert = UIAlertController(title: "Added!", message: "You've added " + TextUI.text! + " to your cabinet", preferredStyle: UIAlertControllerStyle.Alert)
        // add an action (button)
        alert.addAction(UIAlertAction(title: "OK", style: UIAlertActionStyle.Default, handler: nil))
        // show the alert
        self.presentViewController(alert, animated: true, completion: nil)
    }

    func search(str:String) {
        display.removeAll(keepCapacity: false)

        for s in dbIngredients{
            if s.hasPrefix(str){
                display.append(s)
                print(s)
            }
        }
    }

    func tableView(tableView: UITableView,
        numberOfRowsInSection section: Int) -> Int {
            return fetchedIngredient.capacity
    }

    func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCellWithIdentifier("Cell", forIndexPath: indexPath)
        do{
            let fetchedIngredient = try moc.executeFetchRequest(ingredientFetch) as! [Cabinet]
            cell.textLabel?.text = fetchedIngredient[indexPath.row].ingredient
        } catch {
            fatalError("bad things happened: \(error)")
        }
        return cell
    }

    func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
        tableView.deselectRowAtIndexPath(indexPath, animated: true)

        let alert = UIAlertController(title: "Remove " + fetchedIngredient[indexPath.row].ingredient!,
            message: "No more " + fetchedIngredient[indexPath.row].ingredient! + " in your cabinet?",
            preferredStyle: .Alert)

        let deleteAction = UIAlertAction(title: "Remove",
            style: .Default,
            handler: { (action:UIAlertAction) -> Void in
                self.fetchedIngredient.removeAtIndex(indexPath.row)

                do{
                    let fetchedResults = try self.moc.executeFetchRequest(self.ingredientFetch)
                    if let result = fetchedResults[indexPath.row] as? NSManagedObject {
                        self.moc.deleteObject(result)
                        try self.moc.save()
                    }
                }catch{
                    fatalError()
                }
        })

        let cancelAction = UIAlertAction(title: "Cancel",
            style: .Default) { (action: UIAlertAction) -> Void in
        }

        alert.addAction(cancelAction)
        alert.addAction(deleteAction)

        presentViewController(alert,
            animated: true,
            completion: nil)
        TableView.reloadData()
    }


    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }


    /*
    // MARK: - Navigation
    // In a storyboard-based application, you will often want to do a little preparation before navigation
    override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
    // Get the new view controller using segue.destinationViewController.
    // Pass the selected object to the new view controller.
    }
    */
}

Answer 1

由于您的问题不是Core Data，因此您需要使用Table View beginUpdates和EndUpdates来插入行。在buttonPressed函数结束时输入：

do{
    fetchedIngredient = try moc.executeFetchRequest(ingredientFetch) as! [Cabinet]
    self.tableView.beginUpdates()
    let totalIngredients = fetchedIngredient.count
    let newItemIndexPath = NSIndexPath(forRow: totalIngredients-1, inSection: 0)
    self.tableView.insertRowsAtIndexPaths([newItemIndexPath], withRowAnimation: UITableViewRowAnimation.Automatic)
    self.tableView.endUpdates()
} catch {
    fatalError()
}

根据部分中的行数：

func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return fetchedIngredient.count
}

在索引路径的行的单元格上

func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCellWithIdentifier("Cell", forIndexPath: indexPath)
    cell.textLabel?.text = fetchedIngredient[indexPath.row].ingredient
    return cell
}

Answer 2

您的代码存在一些问题。首先，由于您将记录提取到数组中，因此除非您更新数组，否则调用reloadData不会产生任何影响。添加新的核心数据记录与fetchedIngredient数组之间没有自动连接。

有几种方法可以解决这个问题，尽管最常见的方法是在核心数据更新时将记录重新提取到同一个数组中。或者，您可以将代码更改为我们NSFetchedResultsController而不是数组，这将在核心数据更新时自动更新tableView（基于您提供的谓词）。此类为您提供与核心数据的自动连接。

另一个问题是您要在cellForRowAtIndexPath和didSelectRowAtIndexPath中重新获取记录。不应该这样做。相反，您应该只是引用类级fetchedIngredient数组（或NSFetchedResultsController，如果您选择使用它）。

此外，对dataTaskWithRequest的调用在后台运行。从代码中不清楚你是如何使用它的，但事后你有reloadData表明它应该影响tableView。但是因为任务在后台运行，所以在重新加载表之后将运行完成处理程序。因此，您应该在完成处理程序中调用reloadData。因为它将在另一个线程上运行，所以你必须使用：

将它发送到主队列

dispatch_async(dispatch_get_main_queue()) {
  self.tableView.reloadData()
}

更新iOS中的表格视图（Swift）

2 个答案: