Show data in UIPickerView second component based on first component selection

Question

I am using a picker with two components. I want if I select a row in first component on the basis of selected component it shows the value of the corresponding data.

Answer 1

Usually you do it like that. You create a plist file containing the data of all your countries the result is something like

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
  <dict>
    <key>England</key>
    <array>
        <string>Chelsea</string>
        <string>Arsenal</string>
    </array>
    <key>Spain</key>
    <array>
        <string>Barca</string>
        <string>Real</string>
    </array>
 </dict>
</plist>

assuming the following are defined in the properties or somewhere

NSDictionary *countryClubs;
NSArray *countries;
NSArray *clubs;

you then do things like that

- (void)viewDidLoad
{
    [super viewDidLoad];
    NSBundle *bundle = [NSBundle mainBundle];
    NSURL *plistFile = [bundle URLForResource:@"myPListFile" withExtension:@"plist"];
    NSDictionary *dictionary = [NSDictionary dictionaryWithContentsOfURL:plistFile];
    self.countryClubs = dictionary;

    NSString *selectedCountry = [self.countries objectAtIndex:0];
    NSArray *array = [countryClubs objectForKey:selectedCountry];
    self.clubs = array;
}

- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView {
    return 2;
}

- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component {
    if (component == 0)
        return [self.countries count];
    return [self.clubs count];
}

- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row
        forComponent:(NSInteger)component {
    if (component == 0)
        return [self.countries objectAtIndex:row];
    return [self.clubs objectAtIndex:row];
}

- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row
       inComponent:(NSInteger)component {
       if (component == 0) {
         NSString *selectedCountry = [self.countries objectAtIndex:row];
         NSArray *array = [countryClubs objectForKey:selectedCountry];
         self.clubs = array;
         [picker selectRow:0 inComponent:1 animated:YES];
         [picker reloadComponent:1];
    }
}

This should help you. I hope there is not to much typo mistakes but you should at least get the general idea.

Answer 2

Look at this, i think it can help you

1. First of all make sure that you have connected your picker with IBOutlet .

2. Still if you get the issue you can use

[thePickerView reloadComponent:(NSInteger)component];

instead of

[picker reloadComponent:(NSInteger)component]; 

Answer 3

I think the problem is in your didSelectRow method. You check which country is already selected (in country_flag) before allowing the selection of a new country. I don't think there's any reason to do this.

Allow any country to be selected. Then set country_flag based on the row that was selected.

Just do country_flag = row+1;

You can then have your if statements to set up your label if that's important.

Answer 4

your code.. with minor modifications..

didSelectRow

- (void)pickerView:(UIPickerView *)thePickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component {

    if (component == 0) {
        club=[[NSString alloc] initWithFormat:@"%@" , [Nations objectAtIndex:row]];
        [pickerView reloadComponent:1];
          }

}

after that...

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

    if(component ==0)
    {
        return [Nations count];
    }
    else {
        if ([club isEqualToString:@"Espana"]) {
            return [Espana count];
        }
        if ([club isEqualToString:@"Germany"]) {
            return [Germany count];
        }
        // if...
       else  {
            return [England count];
        }
    }

    return 0;
}

and

- (NSString *)pickerView:(UIPickerView *)thePickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component {
    if(component ==0)
    {
        return [Nations objectAtIndex:row];
    }
    else {
        if ([club isEqualToString:@"Espana"]) {
            return [Espana objectAtIndex:row];
        }
        if ([club isEqualToString:@"Germany"]) {
            return [Germany objectAtIndex:row];
        }
        //if....
      else  {
            return [England objectAtIndex:row];


        }
    }

    return 0;
    }

UPD

in h file I have

@interface ViewController : UIViewController <UIPickerViewDataSource, UIPickerViewDelegate> {

    IBOutlet UIPickerView *pickerView;
    NSMutableArray *arrayColors;
    NSMutableArray *Nations;
    NSMutableArray *England;
    NSMutableArray *Espana;
    NSMutableArray *Germany;
    NSString *club;
}

after that.. you must connect de pickerView to yours ViewController (dataSource and delegate)