回到导航堆栈时，请查看相同的视图控制器问题

Question

我的TableViewController中的单元格是从NSMutableArray属性 - itemList 填充的。

@interface MenuViewController : UITableViewController <JSONURLConnectionDelegate>

@property (nonatomic,strong) JSONURLConnection *jsonConnection;
@property (nonatomic,strong) NSURL *jsonURL;   
@property (nonatomic,strong) DataBase *db;
@property (nonatomic,strong) NSString *sel_category;
@property int categoryCount;   
@property (nonatomic,strong) NSMutableArray *itemList;    

@end

加载TableViewController时，会调用一个方法从我的SQLite数据库中提取列表。拉出该列表后，将其解析并保存为NSMutableArray属性，重新加载TableView数据，从而动态填充单元格。

根据选择的单元格确定从sqlite数据库中提取的新列表，然后保存到目标控制器的itemList属性。

由于导航堆栈中的segue数量各不相同，并且取决于所选的单元格，因此我通过执行self segue并重新加载新的NSDictionary属性来重新加载相同的TableViewController。

当我向下移动时，一切都很有效。问题是，当我按下后退按钮返回堆栈然后尝试再次返回时。当我将导航堆栈备份到先前加载的视图控制器时，问题似乎是原始属性不再可访问。有没有其他人有这个问题，知道解决方案？我猜它是因为我需要有一个新的我的TableViewController类实例更动态地向下传递，我没有正确地做到这一点。这是我的segue代码：

#pragma mark - Table view delegate

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{    
    NSDictionary *item = [self.itemList objectAtIndex:indexPath.row];

    NSData *jsonData = [[item objectForKey:@"child_categories"] dataUsingEncoding:NSUTF8StringEncoding];
    NSArray *child_categories = [NSJSONSerialization JSONObjectWithData:jsonData options:NSJSONReadingMutableContainers error:nil];

    self.categoryCount  = [child_categories count];
    self.sel_category   = [item objectForKey:@"id"];


    NSString *sql = [[NSString alloc]initWithFormat:@"WHERE parent_category_id = %@ ORDER BY name ASC", _sel_category];
    self.itemList = [self.db getItemsFrom:@"product_category" where:sql];

    if ([child_categories count] > 0)
    {
        [self performSegueWithIdentifier:@"segue1" sender:self];
    }
    else if([child_categories count] == 0)
    {
        [self performSegueWithIdentifier:@"segue2" sender:self];
    }
}

-(void) prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    if([segue.identifier isEqualToString:@"segue1"])
    {
        MenuViewController *mvc = [segue destinationViewController];
        mvc.jsonConnection  = self.jsonConnection;
        mvc.db              = self.db;
        mvc.sel_category    = self.sel_category;
        mvc.categoryCount   = self.categoryCount;
        mvc.itemList        = self.itemList;
        NSLog(@"Segue1");

    }
    else if([segue.identifier isEqualToString:@"segue2"])
    {
        NSLog(@"Segue2");
    }
}

- (BOOL)shouldPerformSegueWithIdentifier:(NSString *)identifier sender:(id)sender
{
    //ignore segue from cell since we we are calling manually in didSelectRowAtIndexPath
    return (sender == self);
}

Answer 1

@property（非原子，强）NSMutableArray * selectedItemList;

我需要添加名为selectedItemList的第二个属性。

@interface MenuViewController : UITableViewController <JSONURLConnectionDelegate>

@property (nonatomic,strong) JSONURLConnection *jsonConnection;
@property (nonatomic,strong) NSURL *jsonURL;   
@property (nonatomic,strong) DataBase *db;
@property (nonatomic,strong) NSString *sel_category;
@property int categoryCount;   
@property (nonatomic,strong) NSMutableArray *itemList;
@property (nonatomic,strong) NSMutableArray *selectedItemList;       

@end

选择单元格时会创建 selectedItemList ，而不是更改当前的itemList属性。

NSString *sql = [[NSString alloc]initWithFormat:@"WHERE parent_category_id = %@ ORDER BY name ASC", _sel_category];
self.selectedItemList = [self.db getItemsFrom:@"product_category" where:sql];

将该属性传递给新的TableViewController。

-(void) prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    if([segue.identifier isEqualToString:@"segue1"])
    {
        MenuViewController *mvc = [segue destinationViewController];
        mvc.jsonConnection  = self.jsonConnection;
        mvc.db              = self.db;
        mvc.sel_category    = self.sel_category;
        mvc.categoryCount   = self.categoryCount;
        mvc.itemList        = self.selectedItemList;
        NSLog(@"Segue1");

    }
    else if([segue.identifier isEqualToString:@"segue2"])
    {
        NSLog(@"Segue2");
    }
}