UIPickerView updating from UISegmentedControl

Question

I'm attempting to update a single UIPickerView with a different NSArray of data based on which Index is selected from a UISegmentedControl. Currently when I change the control the numberOfRowsInComponent does not update, and the titleForRow will only update when scrolling the picker.

The NSArrays are populated within viewDidLoad, and I'm using the reloadAllComponents method upon an IBAction of the SegmentedControl.

@synthesize subnetView, classControl;

-(NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView {

    //One column

    return 1;
}

-(NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component {

    //set number of rows

    if (classControl.selectedSegmentIndex == 0){
        NSLog(@"Class A Rows %d", [classAArray count]);
        return classAArray.count;
    }
    else if (classControl.selectedSegmentIndex == 1){
        return classBArray.count;
    }
    else if (classControl.selectedSegmentIndex == 2){
        return classCArray.count;
    }
    return 0;
}
-(NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component {

    //set item per row

    if (classControl.selectedSegmentIndex == 0){
        NSLog(@"Class A Rows %d", [classAArray count]);
        return [classAArray objectAtIndex:row];
    }
    else if (classControl.selectedSegmentIndex == 1){
        return [classBArray objectAtIndex:row];
    }
    else if (classControl.selectedSegmentIndex == 2){
        return [classCArray objectAtIndex:row];
    }
    return 0; 
}

-(IBAction)classChange{

    [subnetView reloadAllComponents]; 
}

Based on which selector is chosen to be "selected" within interface builder, the picker is loaded with the correct array and number of rows. Based on this code when selecting an array with less elements, the numberOfRowsInComponents is not being updated, and the app will crash when reaching the end of the smaller array.

So my two problems:

1. Updating of elements only occurs when scrolling.
2. The number of rows does not update when performing the reloadAllComponents method.

Thanks for listening!

Answer 1

I've seen this before. Usually it is caused by the pickerview outlet not being connected, effectively calling reloadAllComponents on nothing. But when you scroll the connected data source and delegate methods still work.

This can be easily checked by login the outlet's value using:

NSLog(@"%@",subnetView);

If it logs (NULL) as I expect it will simply connect your IB outlet and you're done.