Implementing a basic callback in Objective C

Question

How does one implement a raw callback in objective C?

I just want to notify a ViewController when one of my UITableViewCell objects(custom cell) detects touch.

I need to notify my RootViewController so that it can create an object of another ViewController and push it on the navigation stack.

pradeepa · Accepted Answer · 2011-02-25 11:16:07Z

1

You can use a custom init method like below for secondVC and store the _sender in global or class variable. like

id sender;

- (id)initWithSender:(id)_sender
{
    self = [super init];
    if (self) {
        sender=_sender;
    }
    return self;
}

from RootVC initialize secondvc as follows and define a method named -(void) touchDetected; in rootvc.

    secondvc=[[SecondVC alloc] initWithSender:self];
    [[self navigationController] pushViewController: secondvc animated:YES];

when the touch is detected in secondvc call, this will notify your rootvc that the touch is detected in secondvc.

[sender touchDetected];

answered Feb 25, 2011 at 11:16

pradeepa

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2 Comments

some_id Over a year ago

This looks like it could work. The thing Is I detect touch in one class(UITableCell) using a gestureRecognizer. I then want to notify VC1 when a touch is detected. and VC1, creates and pushes VC2 onto the navigation stack

some_id Over a year ago

Anyway, I used a similar approach and solved it. Thanks a lot.

visakh7 · Accepted Answer · 2011-02-25 08:50:44Z

0

You can probably override the Table view delegate method didSelectRowAtIndex: to detect the touch.Then u can push the view controller using pushViewController: method of Navigation controller

answered Feb 25, 2011 at 8:50

visakh7

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4 Comments

some_id Over a year ago

I have objects on top of the table which detect touch. so I cant do that.

Ricardo de Cillo Over a year ago

just implement the delegate method didSelectRowAtIndex from the developer.apple.com/library/ios/#documentation/uikit/reference/…

kubi Over a year ago

@Helium3 If you have views on top of the table view capturing touch then 1) how is your cell detecting touch events? and 2) why do you want your cells to detect touch events?

some_id Over a year ago

@kubi: I have my own data source that keeps track of the selected cells. I then remove these from the collection of cells when a user deletes. So because I have these things on top of the tableview, I cannot use the didSelectRow method, I have tried. I need a way of notifying the ViewController which should detect didSelectRowAtIndexPath from my cell object from another class which uses a TapRecognizer to detect touches.

Vijay Shankar · Accepted Answer · 2011-02-25 13:44:30Z

0

If the cell object you are referring is a button then you can do by [button addTarget:self action:@selector(methodYouWantToInvoke)];

answered Feb 25, 2011 at 13:44

Vijay Shankar

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Comments

kubi · Accepted Answer · 2011-02-25 13:51:33Z

0

You need to set your ViewController to be the delegate of your table view, then implement the tableView:didSelectRowAtIndexPath: method. This is sample code directly from Apple.

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
 {
     [tableView deselectRowAtIndexPath:indexPath animated:NO];
     BATTrailsViewController *trailsController = [[BATTrailsViewController alloc] initWithStyle:UITableViewStylePlain];
     trailsController.selectedRegion = [regions objectAtIndex:indexPath.row];
     [[self navigationController] pushViewController:trailsController animated:YES];
     [trailsController release];
}

answered Feb 25, 2011 at 13:51

kubi

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