Compiling shared library project in workspace

When you a shared library project in a workspace and there are category functions, the compilation will fail. To overcome this problem, you need to add "-ObjC" in "Other Linker Flags" as shown below:

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];
}

Updating UI by the background thread

As simple as this:

 // Add to top of file
 #import <dispatch/dispatch.h>

 if ([NSThread isMainThread])
 {
  [self MyMethodName];
 }
 else
 {
  dispatch_sync(dispatch_get_main_queue(), ^{
   //Update UI in UI thread here
   [self MyMethodName];
  });
 }

Reference:

http://www.ios-developer.net/iphone-ipad-programmer/development/threads/updating-ui-controls-on-background-threads

http://www.raywenderlich.com/4295/multithreading-and-grand-central-dispatch-on-ios-for-beginners-tutorial

Showing alert on the screen

In .Net, we are using MessageBox to show the alert on the screen. In iOS, we are going to use UIAlertView.

Below is the sample code copy

UIAlertView *av = [[[UIAlertView alloc] initWithTitle:@"Helo world"

message:@"This is the popup message."  delegate:self cancelButtonTitle:@"OK"

otherButtonTitles:@"Clear", nil]];

[av show];

Why does prepareForSegue occur before didSelectRowAtIndexPath

The content was copied from:
http://stackoverflow.com/questions/10376967/in-ios-app-why-does-prepareforsegue-occur-before-didselectrowatindexpath

Do you have your detail segue attached to the table view cell? Instead, try dragging it between the two view controllers (the one containing the table and the one where you want it to go).

Then perform it manually when tableView:accessoryButtonTappedForRowWithIndexPath:.