在隐式展开可选值 (UICollectionView) 时意外发现 nil

问题描述

我想制作在获取新项目后重新加载其数据的集合视图.但是当我尝试重新加载集合视图时，我收到此错误

I want to make collection view that reloads its data after getting new items. But when im trying to reload collection view im getting this error

这是视图控制器的代码

import UIKit

class GalleryViewController: UIViewController {
var presenter : ViewToPresenterPhotoProtocol?

@IBOutlet var collectionView: UICollectionView!

let reuseIdentifier = "cell"

override func viewDidLoad() {
    super.viewDidLoad()
    presenter?.viewDidLoad()
    // Do any additional setup after loading the view.
}
}

extension GalleryViewController: UICollectionViewDelegate, UICollectionViewDataSource {

func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    return self.presenter?.photos?.count ?? 0
}

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {

    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: reuseIdentifier, for: indexPath) as! PhotoCollectionViewCell

    cell.label.text = self.presenter?.photos?[indexPath.item].name
    cell.backgroundColor = UIColor.yellow

    return cell
}

// MARK: - UICollectionViewDelegate protocol

private func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath) {
    // handle tap events
    print("You selected cell #\(indexPath.item)!")
}
}

extension GalleryViewController: PresenterToViewPhotoProtocol{
func onFetchPhotoSuccess() {
    self.collectionView.reloadData()
}

func onFetchPhotoFailure(error: String) {
    print("View receives the response from Presenter with error: \(error)")
}


}

我不知道如何在故事板的集合视图中正确地重新加载数据，所以如果你能帮我解决这个问题，我将非常感激

I don't know how to properly reload data in storyboard's collection view so I'll be pretty thankful if you'll help me solving this issue

推荐答案

也许你的 GalleryViewController 是在没有 xib/storyboard 的情况下初始化的.

Maybe your GalleryViewController was initialized without xib/storyboard.

如果您使用故事板，请尝试以下操作:

If you're using storyboard try this:

let storyboard = UIStoryboard(name: 'yourStoryboardName', bundle: .main)
let controller = storyboard.instantiateViewController(identifier: "yourControllerIdentifier") as! GalleryViewController

如果您使用的是 xib 试试这个:

If you're using xib try this:

let controller = UIViewController(nibName: "yourControllerNibName", bundle: .main) as! GalleryViewController

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