ios - 为什么数据给我空值？

Question

我正在尝试将 NSDictionary 从 TableViewController 传递到 ViewController。在我的 TableViewController.m 中。我有这段代码可以导航到 ViewController:

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    NSDictionary *objectDict = [dataArray objectAtIndex:indexPath.row];
    NSLog(@"Info: %@", objectDict);
    // Pass object to new page
    //UIViewController * vc = [[UIViewController alloc] init];
    //[self presentViewController:vc animated:YES completion:nil];

    SeeInfoVC *controller = [[SeeInfoVC alloc] init];
    controller.data = objectDict;

    NSString * storyboardName = @"Main";
    UIStoryboard *storyboard = [UIStoryboard storyboardWithName:storyboardName bundle: nil];
    UIViewController * vc = [storyboard instantiateViewControllerWithIdentifier:@"SeeInfoVC"];
    [self presentViewController:vc animated:YES completion:nil];

在我的 ViewController.h 中我有:

@interface SeeCardVC : UIViewController
{
    NSDictionary *data;
}
@property (nonatomic, retain)NSDictionary *data;


@end

然后我尝试在 ViewController.m 中记录 data:

@implementation SeeCardVC
@synthesize data;

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    NSLog(@"Info: %@", data);

}

但它只给我 null :(我究竟做错了什么？

Answer 1

让我们看看您的代码在这里做了什么:

// Create new controller, assign objectDict to data property
SeeInfoVC *controller = [[SeeInfoVC alloc] init];
controller.data = objectDict;

//Get Storyboard name
NSString * storyboardName = @"Main";
//Get Storyboard (BTW, you can do this with self.storyboard)
UIStoryboard *storyboard = [UIStoryboard storyboardWithName:storyboardName bundle: nil];
//Instantiate NEW controller
UIViewController * vc = [storyboard instantiateViewControllerWithIdentifier:@"SeeInfoVC"];
//Present NEW controller
[self presentViewController:vc animated:YES completion:nil];

您创建了一个 Controller 并为其分配了数据，然后不再使用它，而是从 Storyboard 中创建了一个新 Controller ，您没有添加数据并呈现它。

基本上，您创建了两个，将数据设置为一个并呈现另一个。

看到问题了吗？