Objective-C Fundamentals

152 CHAPTER 7 Protocols
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UITableViewCellStyleValue1
This type of cell has a black, left-aligned label and a blue, right-aligned label.
This style is used commonly around the iPhone OS, specifically in the Settings
application.
UITableViewCellStyleValue2
This type of cell is similar to a UITableViewCellStyleValue1: a black, leftaligned
label and a blue, right-aligned label. In addition, this view provides a
smaller gray, left-aligned text field under the primary text field. These cells are
seen in the Phone application.
UITableViewCellStyleSubtitle
This type of cell is similar to a UITableViewCellStyleValue2, a black, leftaligned
label and a smaller gray, left-aligned text field under the primary text
field. The blue, right-aligned label isn’t available in this view. These cells are
seen in the iPod application.
While many applications use customized subclasses of UITableViewCell, the standard
cells work well in many cases. The structure for the tableView:cellForRowAtIndex-
Path: is similar for all applications. Apple provides special cell-view retrieval methods
to help with memory management when implementing this method. Let’s look at the
general structure of this method’s implementation, shown in the following listing.
Listing 7.8
Returning table view cells for a table view
- (UITableViewCell *)tableView:(UITableView *)tableView
cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
UITableViewCell *cell;
NSString *reuseID = @"cellID";
Initialize
tableView cell
b
cell = [tableView dequeueReusableCellWithIdentifier:reuseID];
if(cell == nil) {
True if statement
cell = [[[UITableViewCell alloc]
initWithStyle:UITableViewCellStyleDefault
reuseIdentifier:reuseID] autorelease];
NSLog(@"Made a new cell view");
}
}
[[cell textLabel] setText:@"Hello World!"];
return cell;
The most important parts of this code happen on three consecutive lines. The first
part B attempts to initialize the cell that’s being requested from the tableView by
using the dequeueReusableCellWithIdentifier method. This method looks for a
cell that has scrolled off the screen and attempts to reuse it. If it finds a cell that can be
recycled, the cell is initialized; otherwise, the if statement c returns true and d is
c
If true, the cell
is executed d