ios - NSClassFromString 对于 Bundle.main.infoDictionary 返回 nil

Question

我正在以编程方式实现 UITabBarController，但在尝试从 Bundle.main.infoDictionary 检索 Controller 时出现错误!["CFBundleExecutable"]

这是 UITabBarController 的代码:

import UIKit

class ENTabBarController: UITabBarController {

    override func viewDidLoad() {
        super.viewDidLoad()

        addChildViewControllers()
    }

    fileprivate func addChildViewControllers() {
        addChildViewController("ENSwipeViewController", imageName: "TabBar_swipe_")
        addChildViewController("ENSocialViewController", imageName: "TabBar_social_")
        addChildViewController("ENNotificationViewController", imageName: "TabBar_notification_")

    }

    fileprivate func addChildViewController(_ childControllerName: String, imageName: String) {
        let ns = Bundle.main.infoDictionary!["CFBundleExecutable"] as! String

        let cls: AnyClass? = NSClassFromString(ns + "." + childControllerName)

        let vcClass = cls as! UIViewController.Type
        let vc = vcClass.init()


        vc.tabBarItem.image = UIImage(named: imageName)
        vc.tabBarItem.selectedImage = UIImage(named: imageName + "selected")

        let nav = UINavigationController()
        nav.addChildViewController(vc)
        addChildViewController(nav)
    }
}

错误发生在let vcClass = cls as! UIViewController.Type 是:

Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value

这是 ENSwipeViewController 的简单代码:

import UIKit

class ENSwipeViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        view.backgroundColor = .red
    }
}

Answer 1

好吧，如果你看一下documentation你会看到它说:

Return Value

The class object named by aClassName, or nil if no class by that name is currently loaded. If aClassName is nil, returns nil.

因此，由于您的 ENSwipeViewController 尚未加载，因此它返回 nil...