Question

我知道有类似的线程，我在网上搜索了很多，我尝试了很多东西，但我仍然无法使它工作。当用户点击UITableView的附件按钮时，我试图将字符串的值从一个视图控制器传递到另一个视图控制器。转换正常，但在目标视图控制器中，字符串打印为null。我知道这是一个常见的程序..但似乎没有任何作用。我尝试过可变字符串，复制，保留，强大，为目标和源控制器创建实例。如果有人能为我提供解决方案，我真的很感激。

SourceViewController.h

@property (nonatomic,strong) NSString*reference; // I have tried retain, copy, nsmutablestring also

SourceViewController.m

#import "DestinationViewController.h"


    - (void)tableView:(UITableView *)tableView accessoryButtonTappedForRowWithIndexPath:(NSIndexPath *)indexPath {

        self.reference = [[NSString alloc] initWithString:[allreferences objectAtIndex:[indexPath row] - 1]];

        NSLog(@"%@", self.reference); // it prints the value correctly

        DestinationViewController * destinationViewController = [[DestinationViewController alloc] init];

        destinationViewController.reference = [NSMutableString stringWithString:self.reference];


        NSString * storyboardName = @"MainStoryboard";
        UIStoryboard *storyboard = [UIStoryboard storyboardWithName:storyboardName bundle: nil];
        UIViewController * vc = [storyboard instantiateViewControllerWithIdentifier:@"destination"];
        vc.modalTransitionStyle = UIModalTransitionStyleCrossDissolve;
        [self presentViewController:vc animated:YES completion:nil];


    }

DestinationViewController.h

@property (nonatomic, retain) NSMutableString * reference; // i have tried strong, copy, nsstring also

DestinationViewController.m

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view.

    NSLog(@"%@", self.reference); // it prints null

    self.sourcevalue.text = self.reference;  // assigning the value to a label


}

解答：

最后修好了。问题是我的过渡。

我改变了：

DestinationViewController * destinationViewController = [[DestinationViewController alloc] init];

为：

DestinationViewController * destinationViewController = [self.storyboard instantiateViewControllerWithIdentifier:@"destination"];

还将过渡更改为：

 [self presentViewController:destinationViewController animated:YES completion:nil];

Answer 1

您正在将字符串设置为viewcontroller并显示另一个。

在你的故事板中你是否将viewcontroller的类设置为“DestinationViewController”？

尝试这样的事情：

- (void)tableView:(UITableView *)tableView accessoryButtonTappedForRowWithIndexPath:(NSIndexPath *)indexPath {

        self.reference = [[NSString alloc] initWithString:[allreferences objectAtIndex:[indexPath row] - 1]];

        NSLog(@"%@", self.reference); // it prints the value correctly

/* This is wrong!
            DestinationViewController * destinationViewController = [[DestinationViewController alloc] init];

            destinationViewController.reference = [NSMutableString stringWithString:self.reference];
*/
        NSString * storyboardName = @"MainStoryboard";
        UIStoryboard *storyboard = [UIStoryboard storyboardWithName:storyboardName bundle: nil];
        UIViewController * vc = [storyboard instantiateViewControllerWithIdentifier:@"destination"];
        vc.modalTransitionStyle = UIModalTransitionStyleCrossDissolve;
        // Cast vc to the real class
        DestinationViewController * destinationViewController = (DestinationViewController*)vc;
        destinationViewController.reference = [NSMutableString stringWithString:self.reference];

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

我没有更改所有代码，所以如果你粘贴它应该可以工作，但我建议你把你的属性恢复到强和NSString。

通过表格附件按钮将字符串值传递给不同的视图控制器

1 个答案: