Showing drop down list

In iOS, there is not "combo box" or "drop down list" control as compare to Windows programming. But, there is a way to achieve this.

Below is the screen snapshot that tells you that yes, there is a way to show the drop down list when the user clicks on the "Choose.." button.

First, you have to add a table view controller to the Storyboard and set its' Identifier to "testTableView".

After that (in this new table view controller), you have to populate the data through the numberOfRowsInSection and cellForRowAtIndexPath method. Nothing special here.

In the didSelectRowAtIndexPath, you have to pass the user selection back to the "main view". "setSelection" is a method in the main view controller (the codes will be shown later).

- (void)tableView:(UITableView *)tableView
    didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    NSString* s = [self.data objectAtIndex:indexPath.row];
    [self.main_view setSelection:s];
}

In the viewDidLoad, you have to write some code to control the popover size.

    CGRect rect = [self.tableView rectForSection:0];
    self.contentSizeForViewInPopover = CGSizeMake(200,
                                                  rect.size.height + 20);

In the .h class of the main view, you have to add the UIPopoverControllerDelegate protocol and also a popover controller variable.

   @interface CViewController : UIViewController<UIPopoverControllerDelegate>
   @property(strong)UIPopoverController* popover_controller;

In the .m file of the main view, you have to add two method for the above protocol.

   - (BOOL)popoverControllerShouldDismissPopover:(UIPopoverController *)popoverController{
        return YES;
   }

   - (void)popoverControllerDidDismissPopover:(UIPopoverController *)popoverController{
      //do cleanup here, if any. 
   }

Through the StoryBoard, select the main view and you have to add the button reference and handle the TouchDown (like click event in the Windows programming). The codes are shown as below:

- (IBAction)choose_btn_onclick:(id)sender {
    if(self.popover_controller == nil)
    {
        CTestViewController* vc =[self.storyboard instantiateViewControllerWithIdentifier:@"testTableView"];
        vc.main_view = self;
       
        UIPopoverController* popover= [[UIPopoverController alloc] initWithContentViewController:vc];
        popover.delegate = self;  
        self.popover_controller = popover;
    }
   
    CGRect popover_rect = [self.view convertRect:[choose_btn frame]
                                        fromView:[choose_btn superview]];

    [self.popover_controller presentPopoverFromRect:popover_rect
                                             inView:self.view
                           permittedArrowDirections:UIPopoverArrowDirectionAny
                                           animated:YES];
}

The popover controller will pass the user selection through this method:

-(void)setSelection:(NSString*)s
{
    self.choose_btn.titleLabel.text = s;
    [self.popover_controller dismissPopoverAnimated:YES];
}