Ios 在viewDidLoad和ViewDidDisplay之间传递数据

我想知道如果在viewDidLoad中有条件地创建了一个值，并且没有初始化，那么如何在viewDidLoad和ViewDidDisplay之间传递该值

override func viewDidLoad() {
    if let foo = self.foo {
        let webView = UIWebView(frame: self.view.frame)
        scrollView.addSubView(webView)
    }
}

override func viewDidAppear() {
    // How do I use my conditionally created webView here?
    func doSomething(webView: UIWebView) {
        // Do stuff
    }
}

---

两个方法都在同一范围内-它们位于同一类实例内，您可以使用实例变量，例如：

fileprivate var webView: UIWebView?

override func viewDidLoad() {
    super.viewDidLoad()

    if let foo = self.foo {
        let webView = UIWebView(frame: self.view.frame)
        scrollView.addSubView(webView)

        self.webView = webView
    }
}

override func viewDidAppear() {
    super.viewDidAppear()

    if let webView = self.webView {
       // do something with my webView
    }
}

---

只需将

webView

移动到类范围，您就可以在类中的任何地方访问它

class MyClass : UIViewController
{

    var webView : UIWebView?

    override func viewDidLoad() {
        if let foo = self.foo {
            webView = UIWebView(frame: self.view.frame)
            scrollView.addSubView(webView)
        }
        else
        {
            webView = nil // or set to some default
        }
    }

    override func viewDidAppear() {
        // How do I use my conditionally created webView here?
        if webView != nil
        {
            // Do stuff
        }
    }
}

---

您可以将webView用作全局变量

let webView : UIWebview {
    return UIWebView(frame: self.view.frame)
}

override func viewDidLoad() {
    if let foo = self.foo {
        scrollView.addSubView(webView)
    }
}
override func viewDidAppear() {
    doSomething()
}

func doSomething() {
    // Do stuff
}

或者您可以访问scrollview子视图

for subview in scrollView.subviews {
    if subview is UIWebview {
        doSomething(webview: subview as! UIWebView)
    }
}

---

您可以将webView设置为全局变量：

var webView : UIWebView?
    override func viewDidLoad() {
        if let foo = self.foo {
            self.webView = UIWebView(frame: self.view.frame)
            scrollView.addSubView(self.webView!)
        }
    }

    override func viewDidAppear() {
        // How do I use my conditionally created webView here?

        func doSomething(webView: UIWebView) {
            // Do stuff
        }

        if let myWebView = self.webView{

            doSomething(webView: myWebView)

        }

    }

一种更好的类似di方法：

var webView : UIWebView?
    override func viewDidLoad() {
        if let foo = self.foo {
            self.webView = UIWebView(frame: self.view.frame)
            scrollView.addSubView(self.webView!)
        }
    }

    override func viewDidAppear() {
        // How do I use my conditionally created webView here?

        if let myWebView = self.webView{

            self.doSomething(webView: myWebView)

        }

    }

    func doSomething(webView: UIWebView) {
        // Do stuff
    }

试试这个

    class ViewController
    {
         //Init glabal variable
         let webView:UIWebView? = nil

          override func viewDidLoad() 
          {
             if let foo = self.foo {
               webView = UIWebView(frame: self.view.frame)
               scrollView.addSubView(webView)
          }

          override func viewDidAppear() 
          {
              if(webView != nil)
              {
                  func doSomething(webView: UIWebView) 
                  {
                     // Do stuff
                   }
              }
         }
   }

---

实例变量。谢谢，使用可能永远不会使用的全局变量有什么缺点吗？@patrikqvarnstrom的“全局变量”实际上是指属性吗？这是对资源的浪费，但Xcode会告诉您是否从未使用过属性（它还会告诉您

var

是否应该是

let

，因为它从未发生过变异）。

nil

是optionals的默认值。不需要在

else

中再次设置它。真的-我总是试图让代码非常明显和明确-所以有时我会过度使用