iPad上的游乐场与此代码崩溃

Question

//: A UIKit based Playground for presenting user interface

import UIKit
import ARKit
import PlaygroundSupport

class MyViewController : UIViewController {

var discoverPanel : UIScrollView!
var ARPanel: UIView!
var ARViewer : ARSCNView!
var helpPanel : UIScrollView!

override func loadView() {
    let names = ["Angel Shark", "Humpback Whale", "Great White Shark", "Bottlenose Dolphin", "Killer Whale", "Goliath Grouper"]
    // add an empty panel to the view controller
    let view = UIView()
    view.backgroundColor = .white

    makeTabBarButtons()

    // initialize panels
    discoverPanel = UIScrollView(frame: CGRect(x: 0, y: 400, width: 100, height: 100))
    ARPanel = UIView(frame: CGRect(x: 150, y: 400, width: 100, height: 100))
    helpPanel = UIScrollView(frame: CGRect(x: 300, y: 400, width: 100, height: 100))
    // set background colors of each panel
    discoverPanel.backgroundColor  = .blue
    ARPanel.backgroundColor = .red
    helpPanel.backgroundColor = .orange

    view.addSubview(discoverPanel)
    view.addSubview(ARPanel)
    view.addSubview(helpPanel)
    self.view = view
}

func makeTabBarButtons()
{
    /* Makes all of the tab bar buttons */
    let discoverButton = UIButton(frame: CGRect(x: 0, y: 0, width: 40, height: 40))
    let ARButton = UIButton(frame: CGRect(x: 150, y: 0, width: 40, height: 40))
    let helpButton = UIButton(frame: CGRect(x: 300, y: 0, width: 40, height: 40))

    /* Make all the tab bar buttons */
    let discoverIconURLString = "https://lh3.googleusercontent.com/KPBfI_GChcO22uMUFBwjGg0aO1iXqUIOVcmoKPgs37rYH2RqdeM3ESnJX7Gr3s2cveqT4qwpjvBrS2pWl0mozikD5Vi268T9F13yCxh6YbbjOlZF8SgheOn_ujl5XDSonaiNLo435m7celkQ_kBlkXXSPqMPONu2ZUVb_LSFwLf9YxUPfFw-ShTzJGl2lWdUMPpA2qHfAIbhbrSkPa3-8-w38D1lKR5z2NNOte6S6NuWsapgRQyR21noHgzXIyXOKquPrVmn9PCwz938MBuH4x09zQqi5x_1HOHhccMvMReg7OGN1UBP87NpF7ALEyYQtHxZYyMSdw9bw9jbV69p9ucpP3zA3kviDEcjI3RIGkcGG47UnGoAS53TqJkg0wSyQUuiyfaaecaXg1kg8y85otINHYOwjVbQlyAfjsbF_athtqAw7xuT7b4OO9Ia4I3JVIRUuKt3GvDjPBUXnXYsqTYkxkL2ENNkTKBbfXxeqZlc8Bhkx47n-GNSHIqZ-gb0Zz44gwcPfm-FQ4mZ1Zk7FNx7f5W4oFXgea-rhXC5DqPjPNw4IIY7WmSI33S9tADc6MMbgBwndxFvk21aS3HC6y7LSOQbRcYff_-G-w17PtcPXrucubGjAzbqlqdYtDz-yOEOgUxwuHVh1ahI278x0Ax8YLmmKKQ=s512-no"
    let discoverIconURL = URL(string: discoverIconURLString)!
    let discoverIconData = try! Data(contentsOf: discoverIconURL)
    let discoverIcon = UIImage(data: discoverIconData)
    discoverButton.contentMode = .scaleAspectFit
    discoverButton.setImage(discoverIcon, for: .normal)

    let ARIconURLString = "https://lh3.googleusercontent.com/emT3b9yhU2o-uz-ZOoomqucgSvylLeWOKYKWbz88tP9zWJSzmIKiADxTWtxD39OiCO_aitwvhIzQ8ICmFbjSuZPTAgvgIEADjN3eft3IQewMVNNLsiKlYPQqnIzAvtn98Do5tBkAcNcY0Li1mX01UQmYyGBx8jF9oCytWirOxOwU68cF00oioqb1x-PVddQiMwcKf1UYtsqSUVXGvwK4G2KkSWOgvXYiH243bzt9PdVvDmz6rVsKqqTUTJewsKyyQf77xF772T8E_tkGQx0g-h8xgKhBhWJI21Zr2v1Z6A_c5xY7arR2ltA-m_yV30afoPm1wCz4dosnqNs7VqCdt2VnhMLhjc-NdFeVYG6b1LAmMDyZOFkTw_xrmnh-Z416ffolEtcZMjuNzEbHwBFwFDsmpMJj-R4SKXrRxtgBrYwRCpG1G3icgI_0G-Kj_rHIHrw4nMfHb708X5_K1SKIyeL5LIThfnxk5JOuS11vX680nFMRu9kmzrP3IdFoJT-6JLYPHtuTgS0kXfcoN7F3QSKd6E2Fl-X8uOxNRSbl9lvKk0I7ymChF5XFHJh5Q1zWCFxczDf8gEdQ1gKGJn4IrzISSwGqw51U2BgGQ6t5qV26CYIoRVeG1tZYUPBdtOdwrOPXgoP6oZDlemcfuJhxJxC4qAV8CSA=s512-no"
    let ARIconURL = URL(string: ARIconURLString)!
    let ARIconData = try! Data(contentsOf: ARIconURL)
    let ARIcon = UIImage(data: ARIconData)
    ARButton.contentMode = .scaleAspectFit
    ARButton.setImage(ARIcon, for: .normal)

    let helpIconURLString = "https://lh3.googleusercontent.com/2KWPU544EUiAK-RvZ86p3H9zMqTBqjaBCb_9Qs7ikq6sMxc_741GRddtnIQFksvOLgNbZtB3QMGIu-A-vhk5KY4U5MVKz0nzwvSh_k8bxndghZt-pcycL6nTxrXgdQmsgY-Lcm2y_5ju1CRLUsnfJXPPWv4jNN2JicB4Vx4kxzjyvbmSS7KKIFy3v2TcVpUKYOyvOtPtTftOavph9mIYU7pJIc1_ihjl9KHbuUCpk0OSrgvXgqKq_zLWcFq8TEkI7ryMGytds92HTDEDQ9dWEesIgdWk4lIH-aKkJIiLLRc-qj4SRygc4Lbl5RCELfnhDngbuen2LCS7PS8g2bu3Qsp_9asAW2AImECZ6EoXHSH7mBUHc8cVkG52YKjwqIfOIaGhPN1aO6EcSlHnsyEpH_XpVb10IvDE0q48gx8bCu1OnX91q5tHyCnIyxGDny28VbLDTaoIF2pg6s9YA-opPOLWMwNGg0Hel2I4ZA45iSH7-NICRB4Cg7Ym4Alk3-CB94HETdZv5fUkRCwCMZUYIdyB0-ZhqiruQ1XDN7z01jl0mWnP6gsAQhwHovTivjz-m3LE1_gcvB_KOGWYAlE7L7SPQ1x996ea1PNaP4q8aNXPHKMToKw4xnACqTY6zSSv4l-MBw40g5Wq-URz1vYoG2QPVHTc0HY=s512-no"
    let helpIconURL = URL(string: helpIconURLString)!
    let helpIconData = try! Data(contentsOf: helpIconURL)
    let helpIcon = UIImage(data: helpIconData)
    helpButton.contentMode = .scaleAspectFit
    helpButton.setImage(helpIcon, for: .normal)

    view.addSubview(discoverButton)
    view.addSubview(ARButton)
    view.addSubview(helpButton)
}
}
// Present the view controller in the Live View window
PlaygroundPage.current.liveView = MyViewController()

iPad上的Swits Playgrounds仅适用于此代码。我已经尝试重新保存文件并制作文件的副本，我没有收到任何错误。相反，当我运行代码时，iPad崩溃而没有通知我。我不知道为什么，因为几乎完全相同的代码只是在几个小时之前完美运行。

Answer 1

• 你在makeTabBarButtons()里面打电话给loadView
• makeTabBarButtons()尝试在self.view中添加3个按钮，但尚未加载，所以loadView称
• 递归发生并且很可能导致堆栈溢出，因此应用程序在运行时崩溃

您可以通过将makeTabBarButtons()声明更改为：func makeTabBarButtons(in view: UIView)来修复它，并将其命名为：makeTabBarButtons(in: view)。 这样你就可以打破通话周期。