在打开可选值图像时意外地发现了nil

Question

目标控制器

class CharDetailsViewController: UIViewController {

    @IBOutlet weak var imageView: UIImageView!
    @IBOutlet weak var nameLabel: UILabel!
    @IBOutlet weak var genderLabel: UILabel!
    @IBOutlet weak var houseLabel: UILabel!
    @IBOutlet weak var ancestryLabel: UILabel!

    var image = UIImage()
    var name = String()
    var gender = String()
    var house = String()
    var ancestry = String()

    override func viewDidLoad() {
        super.viewDidLoad()
        imageView.image = image
        nameLabel.text! = name
        houseLabel.text! = house

        // Do any additional setup after loading the view.
    }

源控制器

class CharacterTableViewController: UITableViewController {

    var charactersData = [Character]()
    override func viewDidLoad() {
        super.viewDidLoad()
        loadData()
    }

    func loadData()
    {
        DispatchQueue.main.async {
            Alamofire.request("http://hp-api.herokuapp.com/api/characters").responseJSON(completionHandler: {
                (response) in
                switch response.result
                {
                case.success(let value):
                    let json = JSON(value)
                    print(json)
                    json.array?.forEach({
                        (character) in
                        let character = Character(name: character["name"].stringValue, house:character["house"].stringValue,image:character["image"].stringValue, gender: character["gender"].stringValue, ancestry: character["ancestry"].stringValue)
                        self.charactersData.append(character)
                    })
                    self.tableView.reloadData()
                case.failure(let error):
                    print(error.localizedDescription)
                }
            })
        }
    }
override func tableView( tableView: UITableView, numberOfRowsInSection section: Int) -> Int {

        return charactersData.count
    }


    override func tableView( tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath) as! CharTableViewCell

        cell.nameLabel.text = "Name: " +  charactersData[indexPath.row].name
        cell.houseLabel.text = "House: " + charactersData[indexPath.row].house

        if let imageURL = URL(string: self.charactersData[indexPath.row].image) {
            DispatchQueue.global().async {
                let data = try? Data(contentsOf: imageURL)
                if let data = data {
                    let image = UIImage(data: data)
                    DispatchQueue.main.async {
                        cell.charImageView.image = image
                    }
                }
            }
        }
        return cell
    }

    override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {

        let hpc = storyboard?.instantiateViewController(withIdentifier: "CharDetails") as? CharDetailsViewController

        hpc?.image = UIImage(named: charactersData[indexPath.row].image)! //Error found here

        hpc?.name = charactersData[indexPath.row].name
        hpc?.house = charactersData[indexPath.row].house
        self.navigationController?.pushViewController(hpc!, animated: true)
    }

class Character
{
    var name : String
    var house : String
    var image : String


    init(name: String, house: String, image: String)
    {
        self.name = name
        self.house = house
        self.image = image
    }
}

在打开可选值图像以将图像传递给另一个控制器时，我意外地发现了nil。我检查了网点，他们完全没问题。如上所示，图像作为JSON格式从url数组中获取，它们在表视图上正常工作并在表视图中看到，但它们没有显示在详细信息视图页面上。请帮助我。

Answer 1

你试图强行打开UIImage，这是零。当图像存在于包内并且您想从那里显示时，使用UIImage(named:)方法。

hpc?.image = UIImage(named: charactersData[indexPath.row].image)! //Error found here

在上面的行中，您正在使用UIImage（名为:)！这意味着，你是强行打开它，导致在意外发现nil时崩溃，同时解开一个可选值

解决方案您可以传递与名称和房屋相同的图像名称，

1）更新你的

class CharDetailsViewController: UIViewController {
  // Add this property to hold url string for image. 
  var imageUrlString = String()
}

2）在didSelectRow中，更新代码以传递imageUrlString

hpc?.imageUrlString = charactersData[indexPath.row].image

2）将它放在CharDetailsViewController的viewDidLoad方法中

if let imageURL = URL(string: imageUrlString) {
    DispatchQueue.global().async {
        let data = try? Data(contentsOf: imageURL)
        if let data = data {
            let image = UIImage(data: data)
            DispatchQueue.main.async {
                self.imageView.image = image
            }
        }
    }
}

希望能帮助到你