（iOS + Firebase）无法将图像从UITableViewCell传递到下一个ViewController

Question

I have a UITableView where the data is coming from a Firebase RealtimeDatabase. Once the user selects the row, the data from the row ie: Title, Description and an Image will be taken to the next ViewController.

I'm able to pass the Title and Description but I'm unable to pass the Image.

Here is my code for the UITableView:

import UIKit
import Firebase

class PostTable: UIViewController, UITableViewDelegate, UITableViewDataSource {

    var tableView:UITableView!

    var posts = [Post]()

    override func viewDidLoad() {
        super.viewDidLoad()

        tableView = UITableView(frame: view.bounds, style: .plain)
        view.addSubview(tableView)

        let cellNib = UINib(nibName: "PostTableViewCell", bundle: nil)
        tableView.register(cellNib, forCellReuseIdentifier: "postCell")
        var layoutGuide:UILayoutGuide!

        layoutGuide = view.safeAreaLayoutGuide

        tableView.leadingAnchor.constraint(equalTo: layoutGuide.leadingAnchor).isActive = true
        tableView.topAnchor.constraint(equalTo: layoutGuide.topAnchor).isActive = true
        tableView.trailingAnchor.constraint(equalTo: layoutGuide.trailingAnchor).isActive = true
        tableView.bottomAnchor.constraint(equalTo: layoutGuide.bottomAnchor).isActive = true

        tableView.delegate = self
        tableView.dataSource = self
        tableView.tableFooterView = UIView()
        tableView.reloadData()


        observePosts()
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    func observePosts() {
        let postsRef = Database.database().reference().child("Data")
        print(postsRef)
        postsRef.observe(.value, with: { snapshot in
            var tempPosts = [Post]()

            for child in snapshot.children{

                if let childSnapshot = child as? DataSnapshot,
                    let dict = childSnapshot.value as? [String:Any],
                    let title = dict["title"] as? String,
                    let logoImage = dict["image"] as? String,
                    let url = URL(string:logoImage),
                    let description = dict["description"] as? String{


                    let userProfile = UserProfile(title: title, photoURL: url)
                    let post = Post(id: childSnapshot.key, title: userProfile, description: description, image: userProfile)
                    print(post)
                    tempPosts.append(post)
                }
            }

            self.posts = tempPosts
            self.tableView.reloadData()
        })
    }

    func getImage(url: String, completion: @escaping (UIImage?) -> ()) {
        URLSession.shared.dataTask(with: URL(string: url)!) { data, response, error in
            if error == nil {
                completion(UIImage(data: data!))
            } else {
                completion(nil)
            }
            }.resume()
    }

    func numberOfSections(in tableView: UITableView) -> Int {
        return 1
    }

    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        print(posts.count)
        return posts.count
    }

    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell{
        let cell = tableView.dequeueReusableCell(withIdentifier: "postCell", for: indexPath) as! PostTableViewCell
        cell.set(post: posts[indexPath.row])
        return cell
    }

    func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        let postsInfo = posts[indexPath.row]
        print(postsInfo)

        let Storyboard = UIStoryboard(name: "Main", bundle: nil)
        let DvC = Storyboard.instantiateViewController(withIdentifier: "PostTableDetailed") as! PostTableDetailed
        DvC.getName = postsInfo.title.title
        DvC.getDesc = postsInfo.description
//        DvC.getImg = postsInfo.title.photoURL
        self.navigationController?.pushViewController(DvC, animated: true)
    }
}

Here is the second ViewControler which has the post details:

import UIKit

class PostTableDetailed: UIViewController {

    var getName = String()
    var getDesc = String()

    @IBOutlet weak var Name: UILabel!
    @IBOutlet weak var Description: UILabel!

    override func viewDidLoad() {
        super.viewDidLoad()

        Name.text! = getName
        Description.text! = getDesc     
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

}

I also have a few Models (Post, UserProfile) and Services (UserService and ImageService), please let me know if that is required to break down this problem.

Answer 1

if you have the imageUrl, all you need is to pass it from PostTable to PostTableDetailed and download the image.

   // PostTable
       func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
            let postsInfo = posts[indexPath.row]
            print(postsInfo)

            let Storyboard = UIStoryboard(name: "Main", bundle: nil)
            let DvC = Storyboard.instantiateViewController(withIdentifier: "PostTableDetailed") as! PostTableDetailed
            DvC.getName = postsInfo.title.title
            DvC.getDesc = postsInfo.description
            DvC.getImg = postsInfo.photoURL
            self.navigationController?.pushViewController(DvC, animated: true)
        }

// PostTableDetailed
class PostTableDetailed: UIViewController {

    var getName = String()
    var getDesc = String()
    var imageUrl = ""

    @IBOutlet weak var Name: UILabel!
    @IBOutlet weak var Description: UILabel!
    @IBOutlet weak var imageView: UIImageView!


    override func viewDidLoad() {
        super.viewDidLoad()

        Name.text! = getName
        Description.text! = getDesc 
        updayeImage()    
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

 private func updateImage() {
        URLSession.shared.dataTask(with: URL(string: self.imageUrl)!) { data, response, error in
            if error == nil, let data = data {
                imageView.image = UIImage(data: data)
            } 
            }.resume()
    }

}

The image will be shown when the task will complete. so I suggest for you to add a spinner to the imageView.

Answer 2

In PostDetail ViewController do like this

import UIKit

class PostTableDetailed: UIViewController {

    var getName = String()
    var getDesc = String()
    var getImg = String()

    @IBOutlet weak var Name: UILabel!
    @IBOutlet weak var Description: UILabel!
    @IBOutlet weak var ImageContainer: UIImageView!

    override func viewDidLoad() {
        super.viewDidLoad()

        Name.text! = getName
        Description.text! = getDesc    
        if let image = getImage(url: getImg) { (image)
            ImageContainer.image = image 
        }

    }

    override func didReceiveMemoryWarning() {
         super.didReceiveMemoryWarning()
         // Dispose of any resources that can be recreated.
    }

    func getImage(url: String, completion: @escaping (UIImage?) -> ()) {
        URLSession.shared.dataTask(with: URL(string: url)!) { data, response, error in
            if error == nil {
                completion(UIImage(data: data!))
            } else {
                completion(nil)
            }
        }.resume()
    }

}

Answer 3

First of all, you can use this code to download the image:

let imageCache = NSCache<AnyObject, AnyObject>()

extension UIImageView {

func downloadImageWithUrlString(urlString: String) -> Void {

    if urlString.count == 0 {
        print("Image Url is not found")
        return
    }

    self.image = nil
    if let cachedImage = imageCache.object(forKey: urlString as AnyObject) as? UIImage {
        self.image = cachedImage
        return
    }

    let request = URLRequest(url: URL(string: urlString)!)
    let dataTask = URLSession.shared.dataTask(with: request) {data, response, error in
        if error != nil { return }
        DispatchQueue.main.async {
            let downloadedImage = UIImage(data: data!)
            if let image = downloadedImage {
                imageCache.setObject(image, forKey: urlString as AnyObject)
                self.image = UIImage(data: data!)
            }
        }
    }
    dataTask.resume()
}
}

Now, if you are using the model that contains Title, Description, and ImageUrlString, then simply pass the selected model object to the next viewController.

In next ViewController, just simply call the same method to download the image which you are using on first ViewController. You don't need to pass the image from VC1 to VC2 because it might be the possible image is not downloaded yet and you select a row to move on next VC.

So here simple thing that pass the model object and calls the image downloading method.