Objective-C Fundamentals

Important protocols
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or in tableView:cellForRowAtIndexPath:, but that isn’t the case. When the
UITableView is delivered a UITableViewCell, Apple modifies certain parts of the cell
to make it fit nicely into the UITableView. When the table view is completely done
doing what it needs to do with the cell, it passes the cell through the following method
for any final modifications. After this method finishes, the cell is put into the table
view and displayed to the user:
- (void)tableView:(UITableView *)tableView
willDisplayCell:(UITableViewCell *)cell
forRowAtIndexPath:(NSIndexPath *)indexPath
7.3.3
The UIActionSheet is a great interface element provided by Apple. It’s used either to
inform the user of an alert that takes over an entire application or to provide a
prompt that a process is being conducted for the user. Examples of this include choosing
a language for an application’s content and informing a user that an application is
uploading some kind of file. Action sheets have a protocol associated with them to
inform the presenting view controller of their activity. Let’s look at the methods that
compose the .
The following method is called when a button from the UIActionSheet is pushed.
After this method executes, the UIActionSheet is automatically dismissed. Here you
respond appropriately to whatever button was selected but don’t have to worry about
returning anything or dismissing the action sheet. That’s all taken care of automatically:
- (void)actionSheet:(UIActionSheet *)actionSheet
clickedButtonAtIndex:(NSInteger)buttonIndex
The following methods are available, providing hooks into the application flow. will-
PresentActionSheet: is called just before the action sheet animation begins, and
didPresentActionSheet: is called as the animation finishes. These different access
points allow developers to get the kind of responsiveness that they’re shooting for:
- (void)willPresentActionSheet:(UIActionSheet *)actionSheet
- (void)didPresentActionSheet:(UIActionSheet *)actionSheet
Like the presentation methods, the following methods provide hooks into the action
sheet when it’s being dismissed. The actionSheet:willDismissWithButtonIndex: is
called just before the action sheet dismissal animation begins, and actionSheet: did-
DismissWithButtonIndex: is called as the dismissal animation finishes:
- (void)actionSheet:(UIActionSheet *)actionSheet
willDismissWithButtonIndex:(NSInteger)buttonIndex
- (void)actionSheet:(UIActionSheet *)actionSheet
didDismissWithButtonIndex:(NSInteger)buttonIndex
The following is the final method you need to implement when creating an action
sheet, and it might not be necessary every time you make one. Action sheets, when
they’re being created, allow developers to set a “destructive button title.” If a developer