Question

I have a 2 components, dependent pickerView. I have a preview UIImageView that changes each time the user uses the pickerView (and triggers the didSelectRow:inComponent:). This works just as I expected.

However, I want the pickerView to trigger didSelectRow: when the app launches, so that there is a Preview the moment the user sees the UIImageView. In viewDidLoad, when I try this:

[self pickerView:picker didSelectRow:row inComponent:component]; // row and component have 0 values. 

next thing that happens – the pickerView shows up blank! Remove this line, and it works perfectly again. I tried this as well:

[picker selectRow: row inComponent:component animated:NO];

thinking that it will trigger didSelectRow: however it doesn’t trigger it and my UIImageView remain blank.

Any advice on how to call the didSelectRow: method without the users help?

Update: by the way, the picker is inside another UIView (not the main one). In case it matters.

Answer 1

didSelectRow:... will only be called if a row has been selected by user interaction. If you select a row programmatically with selectRow:... then you have to add you own logic to update other components like the image view.

The principle is valid for many other delegate functions, such as e.g. tableView:didSelectRowAtIndexPath:.