将代码移至单独的功能时遇到麻烦

如何解决将代码移至单独的功能时遇到麻烦

在GameViewController的 viewDidLoad（）函数中，我做两件事：

1-我创建了一个子UImyew myView，它已添加到主视图中，

2-我在GameViewController的代码中调用了我的函数addConstraints。

创建GameScene时， self.myView.frame.width 和 self.myView.frame.height 包含正确的值，并遵守safeAreaLayout指南。

我想使代码更清晰，因此将addConstraints函数移到了单独的文件中。但是当我以这种方式运行我的应用程序时， self.myView.frame.width 和 self.myView.frame.height 为零。

所以很好奇我是否以某种方式不正确地翻译了函数，或者这是我不能移出主代码的地方？

第一个块是原始代码，第二个是函数

//located with GameViewControl    
private func addConstraints(){
        var constraints = [NSLayoutConstraint]()
        
        constraints.append(myView.leadingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.leadingAnchor))
        constraints.append(myView.trailingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.trailingAnchor))
        constraints.append(myView.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor))
        constraints.append(myView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor))
        NSLayoutConstraint.activate(constraints)
    }

翻译成函数

//called from GameViewControl
    createConstraints(view: myView)
    ....
        
//located outside of GameViewControl
func createConstraints(view: UIView) {
    var constraints = [NSLayoutConstraint]()
                    
    constraints.append(view.leadingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.leadingAnchor))
    constraints.append(view.trailingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.trailingAnchor))
    constraints.append(view.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor))
    constraints.append(view.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor))
                    
    NSLayoutConstraint.activate(constraints)
}

这是GameViewControl的完整文件

import UIKit
import SpriteKit

class GameViewController: UIViewController {
    
    private let myView : UIView = {
        let myView = UIView()
        setViewAttributes(view: myView)
        return myView
    }()

    private func addConstraints(){
         var constraints = [NSLayoutConstraint]()

        //add
         constraints.append(myView.leadingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.leadingAnchor))
         constraints.append(myView.trailingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.trailingAnchor))
         constraints.append(myView.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor))
         constraints.append(myView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor))
        
        //activate
         NSLayoutConstraint.activate(constraints)
     }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        #if DEBUG
            print ("viewDidLoad")
        #endif
        
        if let view = self.view as! SKView? {
            getScreenDimensions (screen: &screenDims)
            view.addSubview(myView)
            addConstraints()

            var scene : GameScene!
            dispatchQueue.main.async { scene = GameScene(size: CGSize(width: self.myView.frame.width,height: self.myView.frame.width))
                scene.anchorPoint = CGPoint(x: 0.0,y: 0.0)
                scene.backgroundColor = .clear
                scene.scaleMode = .aspectFit
                view.isHidden = false
                view.presentScene(scene)
            }
            view.ignoresSiblingOrder    = true
            view.showsFPS               = true
            view.showsNodeCount         = true
            view.showsPhysics           = true
        }
    }
    
    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()

        #if DEBUG
            print ("GVC viewDidLayoutSubviews")
        #endif

        myGlobalVars.sceneRect = view.frame
        
        if #available(iOS 11.0,*) {
            myGlobalVars.topSafeArea    = view.safeAreaInsets.top
            myGlobalVars.bottomSafeArea = view.safeAreaInsets.bottom
        } else {
            myGlobalVars.topSafeArea    = topLayoutGuide.length
            myGlobalVars.bottomSafeArea = bottomLayoutGuide.length
        }
    }
    
    override var shouldAutorotate: Bool {
        #if DEBUG
            print ("shouldAutorotate")
        #endif
        return false
    }
    override var supportedInterfaceOrientations: UIInterfaceOrientationMask {
        #if DEBUG
            print ("supportedInterfaceOrientations")
        #endif
        if UIDevice.current.userInterfaceIdiom == .phone {
            return .allButUpsideDown
        } else {
            return .all
        }
    }
    override var prefeRSStatusBarHidden: Bool {
        #if DEBUG
            print ("prefeRSStatusBarHidden")
        #endif
        return false
    }
}

对函数 setViewAttributes 的调用确实将视图传递给了函数，并且我已经验证了该函数可以正常工作。

func setViewAttributes(view: UIView)
{
    view.alpha                = 0.0
    view.frame.size.height    = UIScreen.main.nativeBounds.height
    view.frame.size.width     = UIScreen.main.nativeBounds.width
    view.translatesAutoresizingMaskIntoConstraints = false
    view.backgroundColor      = .clear
}

解决方法

您不能仅仅移动这种功能，因为其中的view变量引用了GameViewController.view。

如果您要进行这样的重构，则可以将此方法移至扩展名并在GameViewController内调用它。

public extension UIView {
    func createConstraints() {
        guard let superview = superview else { return }

        view.translatesAutoresizingMaskIntoConstraints = false
        var constraints = [NSLayoutConstraint]()
                        
        constraints.append(leadingAnchor.constraint(equalTo: superview.safeAreaLayoutGuide.leadingAnchor))
        constraints.append(trailingAnchor.constraint(equalTo: superview.safeAreaLayoutGuide.trailingAnchor))
        constraints.append(bottomAnchor.constraint(equalTo: superview.safeAreaLayoutGuide.bottomAnchor))
        constraints.append(topAnchor.constraint(equalTo: superview.safeAreaLayoutGuide.topAnchor))
                        
        NSLayoutConstraint.activate(constraints)
    }
}

然后应该调用addConstraints()，而不是在viewDidLoad()中调用myView.createConstraints()。它应该和以前一样工作。

您可以从Extensions — The Swift Programming Language阅读有关扩展的更多信息。

而且您也应该阅读此书Programmatically Creating Constraints

,

遍历代码后，我一遍又一遍地意识到，我在之前 viewDidLayoutSubviews 调用了safeAreaLayout例程。现在，我可以将调用移至函数了，并且可以正常工作。现在，我很想知道为什么过早调用它时它为什么能工作。但是也许我应该感谢我发现了一个严重的错误。

因此，现在我的代码看起来与OP中的代码相同，除了有关屏幕尺寸和safeAreaLayout的每个调用都是在 viewDidLayoutSubviews 函数中完成的。

并且addConstraints现在是一个外部函数

override func viewDidLayoutSubviews() {
    super.viewDidLayoutSubviews()

    getScreenDimensions (screen: &screenDims)
    view.addSubview(myView)
    addConstraints()
    myGlobalVars.sceneRect = view.frame
    createConstraints(view: myView)
    
    if #available(iOS 11.0,*) {
        myGlobalVars.topSafeArea    = view.safeAreaInsets.top
        myGlobalVars.bottomSafeArea = view.safeAreaInsets.bottom
    } else {
        myGlobalVars.topSafeArea    = topLayoutGuide.length
        myGlobalVars.bottomSafeArea = bottomLayoutGuide.length
    }
}