未在视图之间正确传递数据

Question

我正在尝试将用户生成的文本从 AuthenticationViewController 发送到 MainProfileViewController。我没有收到错误报告。标签甚至没有出现在 MainProfileViewController 中。插座已正确连接。感谢您的帮助！

    #import <UIKit/UIKit.h>

    @class MainProfileViewController;

    @interface AuthenticationViewController : UIViewController

    {
        MainProfileViewController *mainProfileViewController;
    }

    @property (retain, nonatomic) IBOutlet UITextField *usernameTextField;

    @end



    #import "AuthenticationViewController.h"
    #import "MainProfileViewController.h"

    @interface AuthenticationViewController ()

    @end

    @implementation AuthenticationViewController

    @synthesize usernameTextField;

    - (IBAction)createAccount: (id)sender {
             {
                mainProfileViewController = [[MainProfileViewController alloc] init];
                mainProfileViewController.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;
                mainProfileViewController.userText.text = usernameTextField.text;
                [self presentViewController:mainProfileViewController animated:YES completion:nil];
              }
    }

    @end



    #import <UIKit/UIKit.h>
    #import "AuthenticationViewController.h"

    @interface MainProfileViewController : UIViewController

    {
       UITextField *userText;
    }

    @property (retain, nonatomic) IBOutlet UILabel *resultLabel;
    @property (retain, nonatomic) IBOutlet UITextField *userText;
    @property (retain, nonatomic) NSString *textPass;

    @end




    #import "MainProfileViewController.h"
    #import "AuthenticationViewController.h"

    @interface MainProfileViewController ()

    @end

    @implementation MainProfileViewController
    @synthesize resultLabel, userText, textPass;

    - (void)viewDidLoad
{

    userText.text = textPass;
    [super viewDidLoad];

}
    @end

Answer 1

好的，你做错了一些事情。 首先，您正在实例化 local MainProfileViewController，而不是实例化您有 ivar 指向的那个。

您做错的第二件事是尝试将视图从AuthenticationViewController 发送到MainProfileViewController。你不应该那样做。相反，传递文本本身；否则你只是覆盖指针，什么都不会显示。

- (IBAction)createAccount: (id)sender {
    // DON'T CREATE A LOCAL VARIABLE
    // MainProfileViewController *controller = [[MainProfileViewController alloc] initWithNibName:@"MainProfileViewController" bundle:nil];
    mainProfileViewController = [[MainProfileViewController alloc] initWithNibName:@"MainProfileViewController" bundle:nil];
    mainProfileViewController.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;

    // DON'T TRY SENDING THE VIEW OVER
    // mainProfileViewController.userText = usernameTextField;
    mainProfileViewController.userText.text = usernameTextField.text;
    [self presentViewController:mainProfileViewController animated:YES completion:nil];
}

编辑：我想你不需要对你想要呈现的新视图控制器有一个 ivar……但关键是你不能实例化一个，然后在你没有实例化的那个上设置参数（它将为零）。

Answer 2

检查您的故事板，看看您是否正确连接了 Outlets。 您的视图控制器中应该有一个 IBOutlet 对象，您应该在情节提要中连接它。

还要检查是否将正确的视图控制器类连接到情节提要中的视图控制器

Answer 3

#import <UIKit/UIKit.h>

@class MainProfileViewController;

@interface AuthenticationViewController : UIViewController

{
    MainProfileViewController *mainProfileViewController;
}

@property (retain, nonatomic) IBOutlet UITextField *usernameTextField;

@end



#import "AuthenticationViewController.h"
#import "MainProfileViewController.h"

@interface AuthenticationViewController ()

@end

@implementation AuthenticationViewController

@synthesize usernameTextField;

- (IBAction)createAccount: (id)sender {
         {
                MainProfileViewController *controller = [[MainProfileViewController alloc] initWithNibName:@"MainProfileViewController" bundle:nil];
                controller.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;

                mainProfileViewController.textpass = usernameTextField.text;

                [self presentViewController:controller animated:YES completion:nil];
          }
}

@end



#import <UIKit/UIKit.h>
#import "AuthenticationViewController.h"

@interface MainProfileViewController : UIViewController

{
   UITextField *userText;
}

@property (retain, nonatomic) IBOutlet UILabel *resultLabel;
@property (retain, nonatomic) IBOutlet UITextField *userText;
@property (retain, nonatomic) NSString *textpass;
@end




#import "MainProfileViewController.h"
#import "AuthenticationViewController.h"

@interface MainProfileViewController ()

@end

@implementation MainProfileViewController
@synthesize resultLabel, userText;
- (void)viewDidLoad {
   usertext.text=textpass;
}
@end

Answer 4

您需要在这部分更改您的代码...

 - (IBAction)createAccount: (id)sender 
   {
       mainProfileViewController = [[MainProfileViewController alloc] init];
       mainProfileViewController.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;
       mainProfileViewController.userText.text = usernameTextField.text;
       [self presentViewController:mainProfileViewController animated:YES completion:nil];
   }

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