Question

I am just trying to transfer a simple string from a UILabel in a prototype cell into a label in the next View Controller. Value of label.text in the viewDidLoad of the View Controller is returning (null).

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"Cell";

    mainCell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];

    if (mainCell == nil) {
        mainCell = [[dictionaryTableCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
    }

    NSString* date = [dateArray objectAtIndex:indexPath.row];
    mainCell.viewLabel.text = date;

    return mainCell;
}


- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {

    if ([segue.identifier isEqualToString:@"View Segue"]) {
        NSLog(@"View Load Segue Success");

        ViewController *one = segue.destinationViewController;
        one.label.text = mainCell.viewLabel.text;
    }
}

What am I doing wrong here?

Answer 1

You can use indexPathForSelectedRow:

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {

    if ([segue.identifier isEqualToString:@"View Segue"]) {

        ViewController *one = segue.destinationViewController;

        NSIndexPath *indexPath = [self.tableView indexPathForSelectedRow];

        one.textProperty = [dateArray objectAtIndex:indexPath.row];
    }
}

Or you can also use sender if your segue is from the cell to the next scene, e.g.:

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    if ([segue.identifier isEqualToString:@"View Segue"])
    {
        ViewController *one = segue.destinationViewController;

        NSAssert([sender isKindOfClass:[UITableViewCell class]], @"Not cell");

        UITableViewCell *cell = sender;
        NSIndexPath *indexPath = [self.tableView indexPathForCell:cell];

        one.textProperty = [dateArray objectAtIndex:indexPath.row];
    }
}

Two things to note:

1. As a matter of good programming style, I am not retrieving the text value from the cell. I’m retrieving the text value from the model. You should not be relying upon the view for information to be passed along. Go back to the model, the original source of the information.

2. Do not set the text property of the label in the destination controller directly. The controls of the destinationController have not been created yet. You should defer setting controls until the destinationController‘s viewDidLoad. So, instead, create a NSString property in the destination controller:

   @property (nonatomic, strong) NSString *textProperty;
   

   Clearly, you should use a more descriptive name than textProperty, but hopefully you get the idea. Anyway, prepareForSegue can set this new property and the viewDidLoad of the destination controller should then use that NSString property to populate the text property of the UILabel, e.g.:

   - (void)viewDidLoad
   {
       [super viewDidLoad];
   
       self.label.text = self.textProperty;
   }