Objective c swift 3-未显示子类视图控制器

在我的Swift 3/Obj-C应用程序中，我在显示Swift视图控制器时遇到问题，该控制器是和Obj-C类的子类

以下代码可以完美地工作：

NavigationController.swift

func myMethod(){
    ...
    let vc = ParentViewController.init(someParameter: parameter) // << results in desired screen
    vc?.stringProperty = "someString"
    self.pushViewController(vc!, animated: true)
}

func myMethod(){
    ...
    let vc = SubClassedViewController.init(someParameter: parameter) // << results in blank screen
    vc?.stringProperty = "someString"
    self.pushViewController(vc!, animated: true)
}

class SubClassedViewController: ParentViewController
{
    // nothing in this file yet
}

ParentViewController.h

@interface SuperParentViewController : UIViewController 
     @property (nonatomic, strong) NSString *stringProperty;
     - (instancetype)initWithSomeParameter:(SomeClass *)someParameter;
@end

@interface ParentViewController : SuperParentViewController
     // numerous properties are declared here
@end

ParentViewController.m

@implementation ParentViewController
    ...

    - (void)viewDidLoad{
        [super viewDidLoad];
        // a bunch of properties are set
    }

    - (void)viewWillAppear:(BOOL)animated{
        [super viewWillAppear:animated];
        // more properties are set
    }

    ...
@end

但是，如果我将ParentViewController子类化，并尝试显示子类“subclass ViewController”，这将导致屏幕上只显示导航栏项；屏幕的其余部分为空白：

NavigationController.swift

func myMethod(){
    ...
    let vc = ParentViewController.init(someParameter: parameter) // << results in desired screen
    vc?.stringProperty = "someString"
    self.pushViewController(vc!, animated: true)
}

func myMethod(){
    ...
    let vc = SubClassedViewController.init(someParameter: parameter) // << results in blank screen
    vc?.stringProperty = "someString"
    self.pushViewController(vc!, animated: true)
}

class SubClassedViewController: ParentViewController
{
    // nothing in this file yet
}

---

有人能告诉我为什么SubassedViewController无法显示与ParentViewController相同的内容吗？

问题是ParentViewController与.xib文件关联（单击.xib文件->转到标识检查器->在自定义类下，您将找到“ParentViewController”）。因此，当子类化ParentViewController以创建SubassedViewController类时，我还需要使用以下代码来初始化相同的.xib文件：

（Swift 3）

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我将检查是否调用了超类中的所有视图循环方法。此外，查看Xcode中的视图层次结构可能会有所帮助。