从 NSDictionary 传递的 iOS 数据为 (null) - JSON 源

Question

好的，所以我使用 push segue 从我的CatViewController -> TopicViewController 中分离出来，我将 JSON 数据拉入 CVC 中的字典，并在 UITableView 中打印出来。一旦用户选择了一行，它应该从选定的NSDictionary 对象中提取categoryID，并使用一组不同的 JSON 数据填充下一个视图，其中replyID == categoryID。

显然不是这样，当我打印出我的passedData NSString 时，它显示为空。

我以为我正确构建了NSDictionary，然后获得了正确的信息，但它似乎并没有按照我的意愿去做。

CatViewController.m

- (void) retrieveData;
{
    NSURL *url = [NSURL URLWithString:getDataURL];
    NSData *data = [NSData dataWithContentsOfURL:url];

    NSLog(@"%@", url);

    jsonArray2 = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:nil];

    NSError *error;
    dict = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:&error];

    for (catDict in dict) {
        catID = catDict[@"categoryID"];
        NSString *catDesc = catDict[@"categoryDesc"];
        NSString *catName = catDict[@"categoryName"];
        NSLog(catID);
    }

    categoryArray = [[NSMutableArray alloc] init];

    for(int i = 0; i < jsonArray2.count; i++)
    {
        NSString *cID = [[jsonArray2 objectAtIndex:i] objectForKey:@"categoryID"];
        NSString *cDesc = [[jsonArray2 objectAtIndex:i] objectForKey:@"categoryDesc"];
        NSString *cName = [[jsonArray2 objectAtIndex:i] objectForKey:@"categoryName"];

        [categoryArray addObject:[[Categories alloc]initWidthCategoryDesc:cDesc andcategoryName:cName andcategoryID:cID]];
    }

    [self.tableView reloadData];
}

---

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    if ([segue.identifier isEqualToString:@"catToTopic"]) {
        TopicViewController *tVC = (TopicViewController *)[segue destinationViewController];
        NSIndexPath *indexPath = [self.tableView indexPathForSelectedRow];

        tVC.passedData = [[[categoryArray objectAtIndex:indexPath.section] valueForKey:@"categoryID"] objectAtIndex:indexPath.row];
    }
}

TopicViewController.m

- (void)viewDidLoad
{
    [super viewDidLoad];

    //test to see what gets passed along
    NSLog(@"%@", passedData);

    self.title = @"Test replies";

    [self retrieveData];

    UITableViewController *tvController = [[UITableViewController alloc] init];
    tvController.tableView = self.tableView;

    self.refreshControl = [[UIRefreshControl alloc] init];
    [self.refreshControl addTarget:self action:@selector(updateTable:) forControlEvents:UIControlEventValueChanged];
    tvController.refreshControl = self.refreshControl;
}

---

输出

2015-03-12 02:29:25.036 Aviato[3081:195303] Login SUCCESS
2015-03-12 02:29:25.314 Aviato[3081:195303] http://tandemenvoy.michaeldvinci.com/forum/categoriesJSON.php
2015-03-12 02:29:25.315 Aviato[3081:195303] 2
2015-03-12 02:29:25.315 Aviato[3081:195303] 5
2015-03-12 02:29:25.315 Aviato[3081:195303] 6
2015-03-12 02:29:25.316 Aviato[3081:195303] 7
2015-03-12 02:29:25.316 Aviato[3081:195303] 8
2015-03-12 02:29:25.316 Aviato[3081:195303] 9
2015-03-12 02:29:25.316 Aviato[3081:195303] 10
2015-03-12 02:29:25.316 Aviato[3081:195303] 11
2015-03-12 02:29:25.317 Aviato[3081:195303] 12
2015-03-12 02:29:25.317 Aviato[3081:195303] 13
2015-03-12 02:29:25.317 Aviato[3081:195303] 14
2015-03-12 02:29:25.317 Aviato[3081:195303] 15
2015-03-12 02:29:27.052 Aviato[3081:195303] (null)
2015-03-12 02:29:27.328 Aviato[3081:195303] http://tandemenvoy.michaeldvinci.com/forum/repliesJSON.php

Answer 1

试试这个代码

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    NSString *categoryIDClicked = [categoryArray objectAtIndex:indexPath.row];
    NSLog("category ID value = %@", categoryIDClicked);
}

如果您想将 categoryIDClicked 用于另一个类，您必须使用全局变量，然后您可以在项目中的任何位置使用。

Answer 2

尝试（假设您尝试传递 categoryId）

Categories* cat = [categoryArray objectAtIndex:indexPath.row];
    tVC.passedData = cat.categoryID ;

改为

tVC.passedData = [[[categoryArray objectAtIndex:indexPath.section] valueForKey:@"categoryID"] objectAtIndex:indexPath.row];

Answer 3

tVC.passedData =[categoryArray objectAtIndex:indexPath.row].catID;

只传递这个值。