Can't set UINavigationItem title programatically on initial load

Question

I'm am performing a segue (via storyboard) from a TableViewController (embedded in a NavigationController) to another TableViewController. I.e Selecting a cell and presenting another TableView on which i would like to display the selected cell's text as the next views title.

I am achieving this however not 100% correctly. On the first initial selection of a cell the navigationItem title is not set. Only once i navigate back and then again forward through that same cell, is the title set.

The first snippet is my first viewController that I'm selecting a cell on where I am setting the destinationViewControllers variable with the selected cells title.

    var valueToPass:String?
    override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
        print("You selected cell #\(indexPath.row)!")

        // Get Cell Label
        let indexPath = tableView.indexPathForSelectedRow!;
        let currentCell = tableView.cellForRowAtIndexPath(indexPath) as UITableViewCell!;

        valueToPass = currentCell.textLabel!.text
    }

    override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {

    if (segue.identifier == "tripSegue") {

        // initialize new view controller and cast it as your view controller
        let viewController = segue.destinationViewController as! TripTableViewController
        // setting the view controllers property that will store the passed value
        viewController.passedValue = valueToPass
    }

}

The second snippet is from the destinationViewController setting the navigationItem title.

var passedValue: String?

override func viewDidLoad() {
    super.viewDidLoad()

    self.navigationItem.title = passedValue
}

@DavidBerry I have edited the post to reflect your comment. See first snippet — Vince, Sep 25 '15 at 02:00
I still don't see where you're setting valueToPass (probably in didSelect...)? — David Berry, Sep 25 '15 at 02:01
Trying move `self.navigationItem.title = passedValue` to somewhere before `viewDidLoad` of viewController 's lifecycle, etc, `viewWillAppear`. — Zigii Wong, Sep 25 '15 at 02:10
@Wongzigii I have tried this previously and did it again now. Doesn't work for me. — Vince, Sep 25 '15 at 02:18

score 1 · Accepted Answer · answered Sep 25 '15 at 02:39

1

This is because prepareForSegue is called before didSelectRowAtIndexPath. So the first time you select a row, valueToPass is nil. prepareForSegue is called while valueToPass is still nil and you pass it, then after you pass that, didSelectRowAtIndexPath is called setting valueToPass to the desired value, which is what's passed the next time you select a row.

You need to do it all in prepareForSegue.

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {

if (segue.identifier == "tripSegue") {
       // Get Cell Label
       let indexPath = self.tableView.indexPathForSelectedRow!;
       let currentCell = self.tableView.cellForRowAtIndexPath(indexPath) as UITableViewCell!;
       // initialize new view controller and cast it as your view controller
       let viewController = segue.destinationViewController as! TripTableViewController
       // setting the view controllers property that will store the passed value
       viewController.passedValue = currentCell.textLabel!.text

    }
}

answered Sep 25 '15 at 02:39

Ahmed Hamed

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Alternatively, do it in `didSelectRow...` and programmatically invoke the segue instead of automatically. – David Berry Sep 25 '15 at 03:02
What would be considered best practice ? – Vince Sep 25 '15 at 04:12
@DavidBerry But I think he would still have to the exact same thing in `prepareForeSegue` whether the segue was performed programmatically or automatically triggered by row selection. – Ahmed Hamed Sep 25 '15 at 06:01
1

@Vince You're welcome glad I could help!! The only thing I would do differently is instead of getting the title from the cell's text label, I'd get it from the data source array that you used to populate the cell's label in the first place. Although I don't have a strong argument for why you shouldn't get it from the cell's label. – Ahmed Hamed Sep 25 '15 at 06:13

Can't set UINavigationItem title programatically on initial load

1 Answers1