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method to respond to user taps and update your to-do list items appropriately.

When a cell gets selected, the table view calls the tableView:didSelectRowAtIndexPath: delegate

method to see how it should handle the selection. In this method, you’ll write code to update the to-do item’s

completion state.

To mark an item as completed or uncompleted

1.

In the project navigator, select XYZToDoListViewController.m.

2. Add the following lines to the end of the file, just above the @end line:

#pragma mark - Table view delegate

- (void)tableView:(UITableView *)tableView

didSelectRowAtIndexPath:(NSIndexPath *)indexPath

{

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Tutorial: Add Data

Mark Items as Completed

}

Try typing the second line instead of just copying and pasting. You’ll find that code completion is one of

the great time-saving features of Xcode. When Xcode brings up the list of potential completions, scroll

through the list until you find the one you want and then press Return. Xcode inserts the whole line for

you.

3.

You want to respond to taps but not actually leave the cell selected. Add the following code to deselect

the cell immediately after selection:

[tableView deselectRowAtIndexPath:indexPath animated:NO];

4.

Search for the corresponding XYZToDoItem in your toDoItems array.

XYZToDoItem *tappedItem = [self.toDoItems objectAtIndex:indexPath.row];

5.

Toggle the completion state of the tapped item.

tappedItem.completed = !tappedItem.completed;

6.

Tell the table view to reload the row whose data you just updated.

[tableView reloadRowsAtIndexPaths:@[indexPath]

withRowAnimation:UITableViewRowAnimationNone];

Your tableView:didSelectRowAtIndexPath: method should look like this:

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath

*)indexPath

{

[tableView deselectRowAtIndexPath:indexPath animated:NO];

XYZToDoItem *tappedItem = [self.toDoItems objectAtIndex:indexPath.row];

tappedItem.completed = !tappedItem.completed;

[tableView reloadRowsAtIndexPaths:@[indexPath]

withRowAnimation:UITableViewRowAnimationNone];

}

2013-10-22 | Copyright © 2013 Apple Inc. All Rights Reserved.

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Tutorial: Add Data

Mark Items as Completed

Checkpoint: Run your app. The list of items you added in loadInitialData is visible as cells in your table

view. But when you tap items, nothing seems to happen. Why not?

The reason is that you haven’t configured the table view cell to display the completion state of an item. To do

so, you need to go back to the tableView:cellForRowAtIndexPath: method and configure the cell to

display an indicator when an item is completed.

One way to indicate that an item is completed is to put a checkmark next to it. Luckily, table view cells can

have a cell accessory on the right side. By default, there’s no accessory; however, you can change the cell to

display a different accessory, one of which is a checkmark. All you have to do is set the cell accessory based

on the completion state of the to-do item.

To display an item’s completion state