将客观C代码翻译为Swift

Question

我必须将一些Objective-C代码翻译成Swift，我在Swift中是一个新手，在Objective-C中是一个完整的Noob。

这条线路造成了麻烦：

MyStreamingVideoView* view = (MyStreamingVideoView*)self.view;

我用它翻译了它：

let view = self.view as! MyStreamingVideoView

但是我收到了这个错误：

Could not cast value of type 'UIView' (0x19f802608) to 'MyStreamingVideoView' (0x1001ba938)

我要翻译的代码是多一点，所以我粘贴整个代码并告诉你我是如何翻译的：

目标C：

#include <ifaddrs.h>
#include <arpa/inet.h>
#include <net/if.h>

#import "ViewController.h"
#import "RTPReceiver.h"
#import "MyStreamingVideoView.h"

#define LISTEN_PORT 5000

@interface ViewController ()

@property (strong) RTPReceiver* receiver;

@end

@implementation ViewController

- (void) viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];
    NSString* ip = [self findLocalWifiIp];
    NSLog(@"local IP: %@",ip);

    MyStreamingVideoView* view = (MyStreamingVideoView*)self.view;
    view.waiting = YES;

    self.receiver = [[RTPReceiver alloc] initWithLocalIp:ip listenPort:LISTEN_PORT];
    self.receiver.delegate = view;
    [view setNeedsDisplay];

    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(decodingFailed:)
                                                 name:AVSampleBufferDisplayLayerFailedToDecodeNotification
                                               object:self.view.layer];


}

- (void) viewWillDisappear:(BOOL)animated {
    [super viewWillDisappear:animated];
    self.receiver = nil;

    [[NSNotificationCenter defaultCenter] removeObserver:self];

}

- (void) decodingFailed:(NSNotification*)notification {
    NSLog(@"decoding failed: %@",notification.userInfo[AVSampleBufferDisplayLayerFailedToDecodeNotificationErrorKey]);
}


@end

Swift Code：

override func viewWillDisappear(animated: Bool) {
    super.viewWillDisappear(animated)

    //ERROR WITH THIS LINE
    self.receiver = nil

    NSNotificationCenter.defaultCenter().removeObserver(self)
}

override func viewDidAppear(animated: Bool) {
    super.viewDidAppear(animated)

    let ip = RTPTools().findLocalWifiIp()
    print("local IP: \(ip)")

    //ERROR WITH THIS LINE
    let view = self.view as! MyStreamingVideoView
    view.waiting = true

    self.receiver = RTPReceiver(localIp: ip, listenPort: 5000)
    self.receiver.delegate = view
    view.setNeedsDisplay()

    NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(MasterViewController.decodingFailed(_:)), name: AVSampleBufferDisplayLayerFailedToDecodeNotification, object: self.view.layer)

}

func decodingFailed(notification: NSNotification) {
    print("decoding failed: ")
}

感谢您的帮助。