UIPickerView Cascade-like Selection

Question

Is it possible to dynamically filter the selection from one side with the other?

For example

| car types | color |

| Toyota | Blue, Yellow |

| Ford | Green, Orange, Purple |

| Ferrari | Red, Green, Yellow |

So when the UIPickerview is displayed, I can select the different types of cars. Upon selecting the type of car, I want to be able to only choose the specified colors.

At the moment I can just load all the car types and only one range of colors when the UIPickerView is displayed. I don't know if its possible to dynamically generate the right hand side with the option on the left.

Answer 1

It's actually quite simple to do. You need to return the relevant colours for component 1 depending on what is selected in component 0, e.g.:

- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component
    //...
    case 1:
    {
        NSArray *colors = [self colorsWithSelection:self.selectedRow0];
        return colors[row];
    }
    //...
}

Then implement the following:

- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component
{
    if (component == 0)
    {
        self.selectedRow0 = row;
        [pickerView reloadComponent:1];
        dispatch_async(dispatch_get_main_queue(), ^{
            [pickerView selectRow:0 inComponent:1 animated:YES];
        });
    }
}

Obviously this can be optimised, but it shows the idea.