如何使用 Api 在页面视图控制器中的所有视图控制器中下载图片？

Question

我的应用程序中有一个页面视图控制器，这个页面视图控制器有 4 个视图控制器 - 所以我在所有这些页面视图控制器中都有图像视图，我想使用 Json Api 下载这些页面中的图像

这是我的代码，但我在所有视图控制器类中都复制了这段代码，所以我只在这里写一个

func refreshingphoto1() {

    let firstImageURL = URL(string: "http://img.autobytel.com/car-reviews/autobytel/11694-good-looking-sports-cars/2016-Ford-Mustang-GT-burnout-red-tire-smoke.jpg")!

    let session = URLSession(configuration: .default)

    // Define a download task. The download task will download the contents of the URL as a Data object and then you can do what you wish with that data.


    let downloadPicTask = session.dataTask(with: firstImageURL) { (data, response, error) in
        // The download has finished.

        if error != nil {
            print("Error downloading picture")
            self.firstImageJson.image = UIImage(named: "1.jpg")
        } else {

            // No errors found.
            // It would be weird if we didn't have a response, so check for that too.
            if (response as? HTTPURLResponse) != nil {

                print("Downloaded picture with response code")

                if let imageData = data {

                    // Finally convert that Data into an image and do what you wish with it.
                    let image = UIImage(data: imageData)
                    self.firstImageJson.image = image
                    // Do something with your image.

                } else {


                    print("Couldn't get image: Image is nil")
                    self.firstImageJson.image = UIImage(named: "1.jpg")

                }
            } else {
                print("Couldn't get response code for some reason")
                self.firstImageJson.image = UIImage(named: "1.jpg")
            }
        }
    }
    downloadPicTask.resume()
}
}

**这可行，但不完全正确**

这是我的故事板的图片

as you see in the picture I have Page VC2 that is page view controller and four view controllers that connected to the page VC2

Answer 1

您拥有多个 VC 的事实与下载图像的任务无关。

但是，除了缺乏抽象之外，您的做法是正确的：使用 URLSession 和 URLSessionTask 是使用 Apple API 的正确方法。

不过，您可能对以下内容感兴趣；为了抽象事物，很多开发人员使用这个名为 Alamofire 的第三方库，专门针对您的情况 AlamofireImage。

例如使用 AlamofireImage 你只需要这样做

let imageView = UIImageView(frame: frame)
let url = URL(string: "https://httpbin.org/image/png")!
let placeholderImage = UIImage(named: "placeholder")!

imageView.af_setImage(withURL: url, placeholderImage: placeholderImage)