Objective-C Fundamentals

Building an application, complete with bugs
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14.1 Building an application, complete with bugs
Let’s create an application and purposely add some errors so that you can discover,
observe, and resolve them. The application isn’t overly complex, but it helps demonstrate
the debugging tools at your disposal. In Xcode create a new Navigation-based
application named DebugSample, and then replace its RootViewController tableview:
numberOfRowsInSection: and tableView:cellForRowAtIndexPath: methods with
the implementation in the following listing.
Listing 14.1
A sample tableview implementation with intentional bug
- (NSInteger)tableView:(UITableView *)tableView
numberOfRowsInSection:(NSInteger)section {
}
return 450;
- (UITableViewCell *)tableView:(UITableView *)tableView
cellForRowAtIndexPath:(NSIndexPath *)indexPath {
}
static NSString *CellIdentifier = @"Cell";
UITableViewCell *cell =
[tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
NSLog(@"We are creating a brand new UITableViewCell...");
cell = [[[UITableViewCell alloc]
initWithStyle:UITableViewCellStyleDefault
reuseIdentifier:CellIdentifier] autorelease];
}
NSLog(@"Configuring cell %d", indexPath.row);
cell.textLabel.text =
[[NSString stringWithFormat:@"Item %d", indexPath.row] retain];
return cell;
When you build and run this application, you should see a UITableView consisting of
450 items. You should also notice that, as you flick through the table, it emits a log
message indicating which cell is currently being configured, as shown in figure 14.1.
Figure 14.1 Console output from the DebugSample application: a new log message is
emitted for each cell that’s configured for the UITableView.