从Firebase异步加载图像时出错

Question

我一直试图安静地异步加载图像。 当我为此创建一个新类并构建并运行该应用程序时，运行时日志中会出现错误

// log
Failed to set (borderWidth) user defined inspected property on ...
could not set nil as the value for the key borderWidth.
could not set nil as the value for the key cornerRadius.

用扩展名而不是类很好，图像异步加载，但是这样，我将无法确保在图像视图中加载了正确的图像。

//  cell for item at
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    let cell  = collectionView.dequeueReusableCell(withReuseIdentifier: "subscribeCell", for: indexPath) as! subscribeViewCell

    cell.userID = self.users[indexPath.row].userId
    cell.profileName.text = self.users[indexPath.row].fullName
    cell.profileImage.setupWithImageUrl(imageUrl: self.users[indexPath.row].ImagePath)
    checkFollowers(indexPath : indexPath)
    return cell
}

我在同一个视图控制器中使用的类：

类下载图片：

private var imageCache = [String:UIImage]()

class CustomImageView : UIImageView {

    var lastImageUrl : String?

    func setupWithImageUrl (imageUrl: String) {

        self.contentMode = .scaleAspectFill
        self.clipsToBounds = true
        self.layer.cornerRadius = 14
        self.layer.borderWidth = 0

        lastImageUrl = imageUrl
        if let cachedImage = imageCache[imageUrl] {
            self.image = cachedImage
            return
        }
        guard let url = URL(string: imageUrl) else {
            return
        }
        URLSession.shared.dataTask(with: url) { (data, response, error) in
            if let error = error {
                print(error)
                return
            }
            guard let data = data else {
                return
            }
            guard let image = UIImage(data : data) else {
                return
                }
            imageCache[url.absoluteString] = image
            }
            if (url.absoluteString != self.lastImageUrl) {
            return
            }
            DispatchQueue.main.async {
                self.image = self.image
            }
        }
    }

Answer 1

为什么“通过这种方式”不能确保在图像视图中加载了正确的图像。 我阅读了您的代码，我认为您的代码适合collectionViewController cellForItemAt