未在視圖之間傳遞數據控制器無法解決

Question

我試圖在兩個視圖控制器之間傳遞一個字符串，第一個命名爲DetailController，第二個VideoController。他們使用push segue與按鈕連接。我的「prepareForSegue」方法被調用，但是在VideoController中字符串返回爲null。我一直在這個問題上困擾了很多年，仍然找不到解決方案。任何幫助將不勝感激。

DetailController.m prepareForSegue方法

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender 
{ NSString *myString=self.city.camera; 
    NSLog(@"%@", myString); 
    NSString *see=@"what is going on?"; 
    NSLog(@"%@", see); 

    VideoController *video= (VideoController *) segue.destinationViewController; 
    video.cam= self.city.camera; 

} 

VideoController.m

#import "VideoController.h" 
#import "City.h" 
#import "DetailController.h" 
#import "ViewController.h" 

@interface VideoController() 

@end 

@implementation VideoController 
@synthesize webView,city,cam; 



- (void)viewDidLoad 
{ 
    NSString *see = self.cam; 
    NSLog(@"%@", see); 

    [super viewDidLoad]; 
    // Do any additional setup after loading the view. 

    [self performSelector:@selector(yourMethod) withObject:nil afterDelay:10.0]; 





    NSString * html = [NSString stringWithFormat:@"<img name=\"Cam\" src=\"%@\" width=\"110%%\" height=\"100%%\" alt=\"Live Feed\" style=\"background-color: #000000\" />", cam]; 

    [webView loadHTMLString:html baseURL:nil]; 

} 
-(void)yourMethod 
{ 
    [self.navigationController popViewControllerAnimated:YES]; 
} 

- (void)didReceiveMemoryWarning 
{ 
    [super didReceiveMemoryWarning]; 
    // Dispose of any resources that can be recreated. 
} 

@end 

這裏是當按鈕被按下並且SEGUE發生，我接收消息。如果我正確地閱讀它，那麼（空）會被同一個webView作爲其他兩個字符串返回，當它應該來自不同的webView？我完全失去了與這個問題

2014-04-21 02:20:23.093 webView[47963:1a303] http://admin:*******@192.168.1.80/video.cgi/ 
2014-04-21 02:20:23.094 webView[47963:1a303] what is going on? 
2014-04-21 02:20:23.102 webView[47963:1a303] (null) 

這裏是我的VideoController.h文件，你可以看到SAM設置爲強，我失去的東西嗎？

#import <UIKit/UIKit.h> 
#import "DetailController.h" 
@class City; 
@interface VideoController : UIViewController{ 
IBOutlet UIWebView *webView; 
IBOutlet UIImageView *image; 



} 
@property (strong,nonatomic) City *city; 
@property (strong, nonatomic)NSString * cam; 
@property(nonatomic,retain) UIWebView *webView; 


@end 

Answer 1

見我的評論：

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender 
{ 
    NSString *myString=self.city.camera; 
    NSLog(@"%@", myString); 
    NSString *see=@"what is going on?"; 
    NSLog(@"%@", see); 

    VideoController *video= (VideoController *) segue.destinationViewController; 
    // be sure that self.city.camera is has value 
    // I think you assign nil to video.cam 
    video.cam= self.city.camera; 
} 

Answer 2

確保您的「凸輪」屬性不會有微弱的屬性分配，或者你想之前它可能被釋放。更好的是，發佈VideoController.h代碼。