快速访问标签栏控制器时出错

Question

我在我的应用程序中使用了 UITabBarController。我想从其中一个选项卡的子视图访问我在选项卡栏中定义的变量：

let tabBar = tabBarController as! baseTabBarController

我已经为另一个标签完成了它，它工作正常。但是这一次，我得到了一个错误：

Fatal error: Unexpectedly found nil while unwrapping an Optional value: file /Users/ms/Desktop/invoice/invoice/PreviewViewController.swift, line 36
2020-05-30 18:46:26.511904+0200 Invo[9455:2542848] Fatal error: Unexpectedly found nil while unwrapping an Optional value: file /Users/ms/Desktop/invoice/invoice/PreviewViewController.swift, line 36

请帮忙！谢谢。

这是视图控制器类：

import UIKit
import WebKit

class PreviewViewController: UIViewController {

    @IBOutlet var webPreview: UIWebView!

    var invoiceComposer: InvoiceComposer!
    var HTMLContent: String!

    var invoiceNumber = 0

    override func viewDidLoad() {
        super.viewDidLoad()

        print(invoiceNumber)
    }

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)

        createInvoiceAsHTML()
    }

    func createInvoiceAsHTML() {
        invoiceComposer = InvoiceComposer()

        if let tabBar = tabBarController as? baseTabBarController {
            if let invoiceHTML = invoiceComposer.renderInvoice(invoiceNumber: String(invoiceNumber), invoiceDate: "", recipientInfo: tabBar.customerData[invoiceNumber][0].input, items: tabBar.itemsData[invoiceNumber], totalAmount: tabBar.totalData[invoiceNumber].total) {

                   webPreview.loadHTMLString(invoiceHTML, baseURL: NSURL(string: invoiceComposer.pathToInvoiceHTMLTemplate!)! as URL)
                   HTMLContent = invoiceHTML
            }
            print("works")
        }
        else {
            print("tabBarController is not of type baseTabBarController or either nil ")
        }

    }

}

这是故事板的视图：

Storyboard

这是标签栏控制器的实现：

导入 UIKit

class baseTabBarController: UITabBarController {

     var customerData: [[customerInformation]] = []
     var itemsData: [[Item]] = []
     var totalData: [TotalInformation] = []

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

Answer 1

tabBarController 不是 baseTabBarController 类型或 nil 你可以检查一下

if let tabBar = tabBarController as? baseTabBarController {
print("tabBarController exists and of type baseTabBarController")
} else {
print("tabBarController is not of type baseTabBarController or either nil ")
}