Delete a cell from a UITableView

Press the Edit button and delete the characters that die in Gone with the Wind. Then press Done, which calls the tableView(_:commitEditingStyle:forRowAtIndexPath:) method of the data source. The expression [indexPath] in this method is an array containing the indexPath.

Source code in Goner.zip

1. Class AppDelegate.swift creates a TableViewController and puts it under a UINavigationController to make the TableViewController’s navigation bar visible.
2. Class TableViewController is also the data source, containing the method tableView(_:commitEditingStyle:forRowAtIndexPath:). The Edit/Done button is created by the method viewDidLoad.

Create the project

Select the Goner folder in the Xcode Project Navigator.
File → New → File…
Chose a template for your new file:
iOS Source/Cocoa Touch Class
Next
Choose options for your new file:
Class: TableViewController
Subclass of: UITableViewController
Next
Create

Select Main.storyboard in the Xcode Project Navigator. Open the left pane of the center panel of Xcode as far as

▼ View Controller Scene
   ▶ View Controller
   First Responder
   Exit

Control-click on ViewController.swift in the Xcode Project Navigator and select Delete.
Do you want to move the file “ViewController.swift” to the Trash, or only remove the reference to it?
Move to Trash.

Apostrophe

Scarlett O’Hara looks better with an apostrophe (Unicode \u2019), than with a single quote (Unicode \u0039). I’ll make them bigger so you can see the difference:
O’Hara (apostrophe)
O'Hara (single quote)
Edit → Special Characters… → Punctuation

The view controllers

To display the navigation bar at the top of the window, we have to put a view controller above the table view, and a navigation controller above the view controller. The view controller immediately above a table view must be of a subclass of table view controller. The table view controller will act as the table view’s data source and delegate. It wears three hats: view controller, data source, and delegate.

The data source and the delegate

Our TableViewController serves as the table view’s data source and the table view’s delegate. Since it is the data source, it contains the characters array and the following methods.

1. numberOfSectionsInTableView(_:)
2. tableView(_:numberOfRowsInSection:)
3. tableView(_:cellForRowAtIndexPath:) returns a UITableViewCell
4. tableView(_:commitEditingStyle:forRowAtIndexPath:) modifies the characters array and the table view. Ours deletes one cell.

Since our TableViewController is also table view’s delegate, it can also have the following method. We didn’t bother to write the method, since we’re satisfied with the version of the method that TableViewController inherits from its superclass UITableViewController. This inherited method gives each cell a red minus.

1. tableView(_:editingStyleForRowAtIndexPath:) decides if this cell should be marked with a red minus or a green plus when the table view is in editing mode.

Things to try

1. [Gone to the left with the wind, gone to the right with the wind.] In the tableView(_:commitEditingStyle:forRowAtIndexPath:) method of the data source, change UITableViewRowAnimation.Fade to UITableViewRowAnimation.Left. It used to make a difference in iOS 6, but I don’t see much difference now.


2. [For users unfamiliar with the movie.] Display the red minus only for characters that actually die during the movie. Add the following property and method to the table view’s delegate.

   	let doomed: NSSet = NSSet(array: [
   		"Melanie Hamilton",
   		"Scarlett’s father",
   		"Scarlett’s mother",
   		"Charles Hamilton (1st husband)",
   		"Frank Kennedy (2nd husband)",
   		"Bonnie Butler (S’s daughter)"
   	]);
   

   	override func tableView(tableView: UITableView, editingStyleForRowAtIndexPath indexPath: NSIndexPath)
   		-> UITableViewCellEditingStyle {
   
   		let tableViewCell: UITableViewCell? = tableView.cellForRowAtIndexPath(indexPath);
   		if tableViewCell != nil
   			&& tableViewCell!.textLabel != nil
   			&& tableViewCell!.textLabel!.text != nil
   			&& doomed.containsObject(tableViewCell!.textLabel!.text!) {
   			return UITableViewCellEditingStyle.Delete;
   		}
   		return UITableViewCellEditingStyle.None;
   	}