获取使用storyboard创建的viewcontroller的属性 [英] Get attribute of viewcontroller created with storyboard

问题描述

我目前正在学习swift，我正在尝试从故事板工作中学习实例，但我现在面临的错误并未记录在案。

<我在我的主故事板中创建了一个viewcontroller，我将它的类型指定为我之前调用的自定义类 SimpleNewsViewController ，这里是我班级的代码，它并不复杂：

  class SimpleNewsViewController：UIViewController {
 
 @IBOutlet weak var myImage：UIImageView！ 
 @IBOutlet weak var myLabel：UILabel！ 
 @IBOutlet weak var myText：UITextView！ 
 
 var event：活动！ 
 
覆盖func viewDidLoad（）{
 super.viewDidLoad（）
} 
  

}

在我的主要故事板上，这里是我指定的自定义ViewController：
我的故事板实现

现在问题出现了：在我的代码中我实现了我的ViewController感谢instanciateViewController（标识符：NewsView），然后我尝试在这段代码中设置我的3个属性：

  ... 
让storyboard = UIStoryboard（名称：Main，bundle：nil）
让controller = storyboard.instantiateViewController（withIdentifier：NewsView）为！ SimpleNewsViewController 
 //controller.myImage.image = UIImage（名称：image.jpg）
 //controller.myText.text =这是一个非常长的例子
 //controller.myTitle.text =这是一个标题示例
 self.navigationController？.pushViewController（controller，animated：true）
 ... 
  

如果我取消对三行的评论，我会发错误说：

致命错误：在解包可选值时意外发现nil

IDE还会显示错误代码和线程（如果是可以提供帮助）：
错误

解决方案

在实例化控制器之后，插座尚未连接，您必须声明临时变量并在 viewDidLoad（）中设置插座属性

  ... 
 let sto ryboard = UIStoryboard（名称：Main，bundle：nil）
让controller = storyboard.instantiateViewController（withIdentifier：NewsView）为！ SimpleNewsViewController 
 controller.tempImage = UIImage（名称：image.jpg）
 controller.tempLabel =这是一个非常长的例子
 controller.tempText =这是一个标题示例
 self.navigationController？.pushViewController（controller，animated：true）
 ... 
  

---

  class SimpleNewsViewController：UIViewController {
 
 @IBOutlet weak var myImage：UIImageView！
 @IBOutlet weak var myLabel：UILabel！
 @IBOutlet weak var myText：UITextView！
 
 var tempImage：UIImage？
 var tempLabel =
 var tempText = 
 
 var事件：事件！
 
覆盖func viewDidLoad（）{
 super.viewDidLoad（）
 myImage.image = tempImage 
 myLabel.text = tempLabel 
 tempText.text = tempText 
} 
  

I'm currently learning swift and I'm trying to learn of instanciation from storyboard works, but the error I'm facing now isn't documented very much.

I created a viewcontroller in my main storyboard and I specified it's type as a custom class I called previously SimpleNewsViewController, here's the code of my class, it is'nt complicated:

class SimpleNewsViewController: UIViewController {

@IBOutlet weak var myImage: UIImageView!
@IBOutlet weak var myLabel: UILabel!
@IBOutlet weak var myText: UITextView!

var event: Events!

override func viewDidLoad() {
    super.viewDidLoad()
}

}

On my main storyboard here is the custom ViewController I specified : My Storyboard implementation

Now here's the problem : In my code I instanciate my ViewController thanks to the instanciateViewController(identifier: "NewsView") and then I try to set my 3 attributes like in this piece of code :

...
    let storyboard = UIStoryboard(name: "Main", bundle: nil)
    let controller = storyboard.instantiateViewController(withIdentifier: "NewsView") as! SimpleNewsViewController
    //controller.myImage.image = UIImage(named: "image.jpg")
    //controller.myText.text = "this is an example that can be really long"
    //controller.myTitle.text = "this is a title example
    self.navigationController?.pushViewController(controller, animated: true)
...

If I un-comment the three lines I have an error saying:

Fatal error: Unexpectedly found nil while unwrapping an Optional value

The IDE also displays the error code and the thread (if that can help): The error

解决方案

Right after instantiating the controller the outlets are not connected yet, you have to declare temporary variables and set the outlet properties in viewDidLoad()

...
    let storyboard = UIStoryboard(name: "Main", bundle: nil)
    let controller = storyboard.instantiateViewController(withIdentifier: "NewsView") as! SimpleNewsViewController
    controller.tempImage = UIImage(named: "image.jpg")
    controller.tempLabel = "this is an example that can be really long"
    controller.tempText = "this is a title example
    self.navigationController?.pushViewController(controller, animated: true)
...

---

class SimpleNewsViewController: UIViewController {

@IBOutlet weak var myImage: UIImageView!
@IBOutlet weak var myLabel: UILabel!
@IBOutlet weak var myText: UITextView!

var tempImage : UIImage?
var tempLabel = ""
var tempText = ""

var event: Events!

override func viewDidLoad() {
    super.viewDidLoad()
    myImage.image = tempImage
    myLabel.text = tempLabel
    tempText.text = tempText
}

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