从firebase异步加载图像时出错

Question

一段时间以来，我一直在尝试异步加载图像。 当我为此创建一个新类并构建并运行应用程序时，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.

使用扩展而不是类很好，图像加载异步但是这样我将无法确保在图像视图中加载正确的图像。

//  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
}

我一直在同一个视图控制器中使用的类：

图片下载类：

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“这种方式”无法确保在图像视图中加载正确的图像。我阅读了您的代码，我认为您的代码适用于 collectionViewController cellForItemAt