image - 银联银行 : Can't I download image with a URL?

Question

我想从 URL 加载图像。

我的功能:

func userContentController(_ userContentController: WKUserContentController, didReceive message: WKScriptMessage) {
    if "bigImage" == message.name {
        print(message.body as? String ?? "nothing")
        let urlString = message.body as! String
        print(urlString)
        imageView.downloadedFrom(link: urlString)
    }
    if imageView != nil{
    }
}

我在以下位置遇到错误:imageView.downloadedFrom(link: urlString)

unexpectedly found nil while unwrapping an Optional value

即使我可以收到非零的消息。

顺便说一句，我打开了 ATS.. 真的很想知道发生了什么。

    func getDataFromUrl(url: URL, completion: @escaping (_ data: Data?, _  response: URLResponse?, _ error: Error?) -> Void) {
    URLSession.shared.dataTask(with: url) {
        (data, response, error) in
        completion(data, response, error)
        }.resume()
}

func downloadImage(url: URL) {
    print("Download Started")
    getDataFromUrl(url: url) { (data, response, error)  in
        guard let data = data, error == nil else { return }
        print(response?.suggestedFilename ?? url.lastPathComponent)
        print("Download Finished")
        DispatchQueue.main.async() { () -> Void in
            self.imageView.image = UIImage(data: data)
        }
    }
}

extension UIImageView {
func downloadedFrom(url: URL, contentMode mode: UIViewContentMode = .scaleAspectFit) {
    contentMode = mode
    URLSession.shared.dataTask(with: url) { (data, response, error) in
        guard
            let httpURLResponse = response as? HTTPURLResponse, httpURLResponse.statusCode == 200,
            let mimeType = response?.mimeType, mimeType.hasPrefix("image"),
            let data = data, error == nil,
            let image = UIImage(data: data)
            else { return }
        DispatchQueue.main.async() { () -> Void in
            self.image = image
        }
        }.resume()
}
func downloadedFrom(link: String, contentMode mode: UIViewContentMode = .scaleAspectFit) {
    guard let url = URL(string: link) else { return }
    downloadedFrom(url: url, contentMode: mode)
}

Answer 1

我建议使用图像加载器将图像加载到 UIImageView 中。使用 KFSwiftImageLoader

let imageView : UIImageView!
imageView.loadImage(urlString: imageURL)