图像缓存在获取图像时出现问题 firebase swift iOS

Question

[][！我想使用图像缓存从 Firebase 的下载 url 加载图像我如何才能在我的图像被加载的地方创建继承我想我在某处缺少 OOP 概念。我的图像视图是滑动标签，如何创建一个可以在我的视图上显示图像的实例。

导入 UIKit

导入 Firebase

类 swipeLabelViewController: UIViewController {

@IBOutlet weak var UserAgeText: UILabel!


var user:User? {

    didSet {


        let userNameSwipe = user?.userName

        userNameLabel.text = userNameSwipe

        let userAgeSwipe = user?.userAge

        UserAgeText.text = userAgeSwipe

        guard let profileImageUrl = user?.profileImageUrl else { 

返回 } profileImageView.loadImage(with: profileImageUrl)

        print(profileImageUrl)

  //  let userFetchedImage = user?.profileImageUrl

     //   swipeLabel.image = userFetchedImage

       // self.swipeLabel.image = UIImage(contentsOfFile: profileImageUrl)

     }
}
var profileImageView: CustomImageView = {


    let iv = CustomImageView()


    return iv

}()


var imageI : UIImage!

// var swipepic = CustomImageView()

@IBOutlet weak var swipeLabel: UIImageView!


@IBOutlet weak var userNameLabel: UILabel!




override func viewDidLoad() {


    super.viewDidLoad()


   swipeLabel.image = imageI


    let gesture = UIPanGestureRecognizer(target: self, action: 

选择器(wasDragged(gestureRecognizer:)))

 swipeLabel.addGestureRecognizer(gesture)



 fetchCurrentUserData() 


    }

// 用户模型类``

class User {

// attributes getting users info  so i can set up  from  firebase





var userName:String!


var userAge:String!


var uid:String!


var profileImageUrl: String!

init (uid:String,dictionary:Dictionary) {

self.uid = uid

if let userName = dictionary [ "userName" ] as? String{


    self.userName = userName

}

if let userAge = dictionary [ "userAge" ] as? String{


    self.userAge = userAge
}

如果让 profileImageUrl = dictionary["profileImageURL"] as?字符串 {

  self.profileImageUrl = profileImageUrl

}

}
}

// 最后是图片缓存类customImageView

导入基础

导入 UIKit

var imageCache = String: UIImage

类 CustomImageView: UIImageView {

var lastImgUrlUsedToLoadImage: String?


func loadImage(with urlString: String) {


    // set image to nil


    self.image = nil

    // set lastImgUrlUsedToLoadImage


    lastImgUrlUsedToLoadImage = urlString


    // check if image exists in cache


    if let cachedImage = imageCache[urlString] {


        self.image = cachedImage

        return
    }

    // url for image location




    guard let url = URL(string: urlString) else { return }





    // fetch contents of URL


    URLSession.shared.dataTask(with: url) { (data, response, error) in

        // handle error


        if let error = error {


            print("Failed to load image with error", 

error.localizedDescription) }

        if self.lastImgUrlUsedToLoadImage != url.absoluteString {

            return
        }

        // image data
        guard let imageData = data else { return }



        // create image using image data


        let photoImage = UIImage(data: imageData)



        // set key and value for image cache


        imageCache[url.absoluteString] = photoImage


        // set image

        DispatchQueue.main.async {

            self.image = photoImage
        }

        }.resume()
}

}

没有错误，我只是在我的 swipelabel UIImage 上看不到图像

Answer 1

您需要单独请求从 firebase 返回的 url 下载图像。这是一个游乐场示例：

//: A SpriteKit based Playground

import PlaygroundSupport
import UIKit

enum ImageDownloadError: Error {
  case failedToConvertDataToImage
}

func dowloadImage(from url: URL, completion: @escaping (Result<UIImage, Error>) -> Void) {
  let task = URLSession.shared.dataTask(with: url) { data, response, error in
    guard let image = data.flatMap(UIImage.init(data:)) else {
      return completion (.failure(error ?? ImageDownloadError.failedToConvertDataToImage))
    }
    completion(.success(image))
  }.resume()
}

let imageView = UIImageView()
dowloadImage(from: URL(string: "https://res.cloudinary.com/demo/image/upload/sample.jpg")!) { [weak imageView] result in
  switch result {
  case .failure(let error):
    print(error.localizedDescription)
  case .success(let image):
    imageView?.image = image
  }
}
imageView.frame = .init(origin: .zero, size: .init(width: 300, height: 300))
PlaygroundPage.current.liveView = imageView
PlaygroundPage.current.needsIndefiniteExecution = true