UICollectionView找不到成员

Question

我试图以编程方式在Swift中创建一个UICollectionView。我可以设置它，但是一旦我尝试在自己身上使用更复杂的操作，例如insertItemsAtIndexPath或deleteItemsAtIndexPath时。我得到一个"找不到成员"的错误。更简单的操作，如numberOfSections(如我的示例代码中所示)可以很好地工作。我已经将我的代码与许多其他人的代码进行了比较，但没有发现问题。

MainViewController

import UIKit
import CoreMotion
import MediaPlayer
import SpriteKit
class MainViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegate {

    var containerView : UIView?        
    var collectionView : UICollectionView?        
    var card : UIView?
    var fishArray = NSMutableArray()
    var cellCount = 20
    init(nibName nibNameOrNil: String?, bundle nibBundleOrNil: NSBundle?) {
        super.init(nibName: nibNameOrNil, bundle: nibBundleOrNil)
    }
    override func viewDidLoad() {
        super.viewDidLoad()
        self.view.backgroundColor = UIColor.blackColor()

        ////// COLLECTION VIEW
        var tapGestureRecognizer = UITapGestureRecognizer(target: self, action: "tappiDiTap:")
        var layout = FishFlowLayout()
        collectionView = UICollectionView(frame: CGRectMake(96/2,352/2,1857/2,1117/2), collectionViewLayout: layout)
        collectionView!.delegate = self
        collectionView!.dataSource = self
        collectionView!.addGestureRecognizer(tapGestureRecognizer)
        collectionView!.registerClass(FishCollectionViewCell.self, forCellWithReuseIdentifier: "cellID")
        self.view.insertSubview(collectionView!, belowSubview:scaleBackground!)
        for i in 0..9 {
            fishArray.addObject("Fish: (i)")
        }

    }

    func tappiDiTap(tapGestureRecognizer : UITapGestureRecognizer) {
        if (tapGestureRecognizer.state == .Ended) {
            var initialPinchPoint : CGPoint = tapGestureRecognizer.locationInView(self.collectionView)
            var tappedCellPath : NSIndexPath = self.collectionView!.indexPathForItemAtPoint(initialPinchPoint)
            if (tappedCellPath==nil) {
                self.cellCount = self.cellCount+1
                self.collectionView!.backgroundColor = UIColor.blackColor()
            } else  {
                self.collectionView!.backgroundColor = UIColor.blueColor()
                println(slef.collectionView!.numberOfSections)
            }
        }
    }
    //////////////////COLLECTIONVIEW DELEGATE METHODS
    func collectionView(collectionView : UICollectionView!, numberOfItemsInSection section: Int) -> Int {
        return cellCount
    }
    func collectionView(collectionView : UICollectionView!, cellForItemAtIndexPath indexPath: NSIndexPath!) -> UICollectionViewCell! {
        var cell = collectionView.dequeueReusableCellWithReuseIdentifier("cellID", forIndexPath: indexPath) as FishCollectionViewCell
        return cell
    }
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }
}

鱼流布局

import UIKit
class FishFlowLayout: UICollectionViewFlowLayout {
    init() {
        super.init()
        self.scrollDirection = UICollectionViewScrollDirection.Vertical
        self.itemSize = CGSizeMake(220,270)
       self.minimumLineSpacing = 18
        self.sectionInset = UIEdgeInsetsMake(0,0,0,0)
    }
}

FishCollectionViewCell

import UIKit
class FishCollectionViewCell: UICollectionViewCell {
    init(frame: CGRect) {
        super.init(frame: frame)
        self.layer.cornerRadius = 5
        var card = Card(frame: self.bounds)
        self.addSubview(card)
    }
}

Answer 1

实现deleteItemsAtIndexPath和insertItemsAtIndexPath的关键是需要确保collectionView:numberOfItemsInSection:在删除或插入后返回正确数量的项。例如，如果表当前有10个元素，并且调用deleteItemsAtIndexPath，则需要确保下一次集合视图请求元素数量时返回9，否则将崩溃。集合视图不会为您增加或减少该数字。

Answer 2

您的问题可能是没有展开可选值。

例如，尝试这样做

func controller(controller: NSFetchedResultsController, didChangeObject anObject: AnyObject, atIndexPath indexPath: NSIndexPath?, forChangeType type: NSFetchedResultsChangeType, newIndexPath: NSIndexPath?) {
    switch type {
    case .Insert:
        self.collectionView.insertItemsAtIndexPaths([newIndexPath])
    ...etc
}

会给你错误could not find member 'insertItemsAtIndexPaths'

，它不能。该方法期望[AnyObject]而不是[Optional]

修复打开可选的。

func controller(controller: NSFetchedResultsController, didChangeObject anObject: AnyObject, atIndexPath indexPath: NSIndexPath?, forChangeType type: NSFetchedResultsChangeType, newIndexPath: NSIndexPath?) {
        switch type {
        case .Insert:
            self.collectionView.insertItemsAtIndexPaths([newIndexPath!])
        ...etc
    }