表单加载时如何在文本框中加载字符串？

Question

我正在尝试在加载表单时在文本框中加载字符串。不知何故什么也没出现。有人可以向我解释为什么会这样吗？

let imageCache = NSCache<NSString, UIImage>()

class CustomImageView : UIImageView {

var imageUrlString: String?

func loadImageWithData (urlString: String) {

    imageUrlString = urlString
    if let imageFromCache = imageCache.object(forKey: urlString as NSString){
        self.image = imageFromCache
    }
    image = nil
    let url = URL(string: urlString)
    URLSession.shared.dataTask(with: url!, completionHandler: { (data, response, error) in

        if let err = error {
            print(err.localizedDescription)
        }
        if let data = data {

            DispatchQueue.main.async {
                let imageToCache = UIImage(data: data)
                if self.imageUrlString == urlString {
                    self.image = imageToCache
                }
                imageCache.setObject(imageToCache!, forKey: urlString as NSString)
            }
        }
    }).resume()
}
}

Answer 1

我按照pstrjds的提示创建了一个最小，完整和可验证的示例。原来，我在代码的另一部分出现错误，导致文本框无法加载任何文本。非常感谢。