Swift 加载到TableView的图像错误

这是我第一次将NSCache用于表视图。对于

cellForRow

我调用NSCache加载图像。图像有时是错误的图像。我能做些什么来解决这个问题？如果缓存中不包含它，我会将照片替换为“randomguy”

考虑到以下情况： let cache=NSCache（）

---

这是一种创建自定义图像视图的方法，其中包含一个函数，用于下载图像并将其分配给适当的单元格

let cache = NSCache<NSString, UIImage>()

class CustomImageView: UIImageView {
    var imageURLString: String?

    func startImageDownloadOperation(url: URL) {
        imageURLString = url.absoluteString

        if let cachedVersion = cache.object(forKey: url.absoluteString as NSString) {
            self.image = cachedVersion
        } else {
            let task = URLSession.shared.dataTask(with: url) { (data, response, error) in
                guard error == nil,
                    let response = response as? HTTPURLResponse,
                    response.statusCode == 200 else {
                        DispatchQueue.main.async {
                            self.image = UIImage(named: "default")
                        }
                        return
                }

                DispatchQueue.main.async {
                    if let data = data {
                        let imageToCache = UIImage(data: data)
                        if url.absoluteString == self.imageURLString {
                            self.image = imageToCache
                            cache.setObject(imageToCache!, forKey: url.absoluteString as NSString)
                        }
                    }
                }
            }

            task.resume()
        }
    }
}

let cache=NSCache（）
类CustomImageView:UIImageView{
var imageURLString:String？
func startImageDownloadOperation（url:url）{
imageURLString=url.absoluteString
如果让cachedVersion=cache.object（forKey:url.absoluteString作为NSString）{
self.image=cachedVersion
}否则{
让task=URLSession.shared.dataTask（带：url）{（数据、响应、错误）在
保护错误==零，
let response=响应为？HTTPURLResponse，
response.statusCode==200其他{
DispatchQueue.main.async{
self.image=UIImage（名为“默认”）
}
返回
}
DispatchQueue.main.async{
如果let data=data{
让imageToCache=UIImage（数据：数据）
如果url.absoluteString==self.imageURLString{
self.image=imageToCache
setObject（imageToCache！，forKey:url.absoluteString作为NSString）
}
}
}
}
task.resume（）
}
}
}

为什么有这么多阵列？您只有一个数组，其中每个元素都是一个结构，包含用户名、消息等字段。您需要提供有关如何创建和填充缓存的更多详细信息。请使用数组的模型，在

if else

中执行相同的代码，并使用缓存更新它。SetObjective我认为问题在于我错误地附加了URLARY。

    func photoQuery () {
    for username in self.usernameArray {
        let photoQuery = PFQuery(className: "UserPhoto")
        photoQuery.whereKey("username", equalTo: username)
        photoQuery.findObjectsInBackground(block: { (objects: 
        [PFObject]?,error: Error?) in
        if let objects = objects {
            for object in objects {
                if error == nil {
                let userImageFile = object["photo"] as? PFFileObject
                let urlString = userImageFile?.url as! String

                    if let url = URL(string: urlString) {
                        let data = try? Data(contentsOf: url)
                        if let imageData = data {
            self.messageImageArray.append(UIImage(data:imageData)!)
            self.cache.setObject(UIImage(data:imageData)!, forKey: urlString as 
            NSString)
            self.urlArray.append(urlString as NSString)
            print(self.messageImageArray)
                        }
                    }
            }
        }

            }
        })
    }
}

let cache = NSCache<NSString, UIImage>()

class CustomImageView: UIImageView {
    var imageURLString: String?

    func startImageDownloadOperation(url: URL) {
        imageURLString = url.absoluteString

        if let cachedVersion = cache.object(forKey: url.absoluteString as NSString) {
            self.image = cachedVersion
        } else {
            let task = URLSession.shared.dataTask(with: url) { (data, response, error) in
                guard error == nil,
                    let response = response as? HTTPURLResponse,
                    response.statusCode == 200 else {
                        DispatchQueue.main.async {
                            self.image = UIImage(named: "default")
                        }
                        return
                }

                DispatchQueue.main.async {
                    if let data = data {
                        let imageToCache = UIImage(data: data)
                        if url.absoluteString == self.imageURLString {
                            self.image = imageToCache
                            cache.setObject(imageToCache!, forKey: url.absoluteString as NSString)
                        }
                    }
                }
            }

            task.resume()
        }
    }
}