ios - 通过表格附件按钮将字符串值传递给不同的 View Controller

Question

我知道有类似的线程，我在网上搜索了很多，也尝试了很多东西，但我仍然无法让它工作。当用户单击 UITableView 的附件按钮时，我试图将字符串的值从一个 View Controller 传递到另一个 View Controller 。转换工作正常，但在目标 View Controller 中，字符串打印为空。我知道这是一个常见的程序..但似乎没有任何效果。我尝试了可变字符串、复制、保留、强壮、为目标和源 Controller 创建实例。如果有人能为我提供解决方案，我将不胜感激。

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


}

回答:

终于解决了。问题是我的过渡。

我改变了:

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

到:

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到一个 View Controller 中并呈现另一个 View Controller 。

在您的 Storyboard中，您是否将 View Controller 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，但我建议你将你的属性放回 strong 和 NSString。