Trouble with Cells in UITableView - ios

Question

I'm writing a simple checklist app. I have two UIViewControllers. The first displays the checklist in a UITableView. I'm using a UIBarButtonItem to push a second view onto the stack to add new tasks. All of the tasks are saved in an array.
Everything works great save for one thing.
If I enter edit mode and delete an item from the table view, the item is removed from the table view and the array--this part seems to be working fine. However, after deleting an item, if I tap the bar button item to add a new task, I run into a problem.
My NSLogs tell me that the new item is added to the array, but when I return to the table view, the deleted item shows up instead of the new item. The table view seems to be reusing the dequeued cell (not sure).
What am I doing wrong?
CLCheckListViewController.m
#import "CLCheckListViewController.h"
#import "CLTaskFactory.h"
#import "CLTaskStore.h"
#import "CLAddTaskViewController.h"
#implementation CLCheckListViewController
{
__weak IBOutlet UITableView *checkList;
}
- (id)init
{
self = [super init];
if (self) {
// add five sample tasks
CLTaskFactory *task1 = [[CLTaskFactory alloc] init];
[task1 setTaskName:#"Task 1"];
[task1 setDidComplete:NO];
[[CLTaskStore sharedStore] addTask:task1];
CLTaskFactory *task2 = [[CLTaskFactory alloc] init];
[task2 setTaskName:#"Task 2"];
[task2 setDidComplete:NO];
[[CLTaskStore sharedStore] addTask:task2];
CLTaskFactory *task3 = [[CLTaskFactory alloc] init];
[task3 setTaskName:#"Task 3"];
[task3 setDidComplete:NO];
[[CLTaskStore sharedStore] addTask:task3];
CLTaskFactory *task4 = [[CLTaskFactory alloc] init];
[task4 setTaskName:#"Task 4"];
[task4 setDidComplete:NO];
[[CLTaskStore sharedStore] addTask:task4];
CLTaskFactory *task5 = [[CLTaskFactory alloc] init];
[task5 setTaskName:#"Task 5"];
[task5 setDidComplete:NO];
[[CLTaskStore sharedStore] addTask:task5];
}
return self;
}
- (void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated];
[checkList reloadData];
}
- (void)viewDidLoad
{
[super viewDidLoad];
// create edit button
[[self navigationItem] setLeftBarButtonItem:[self editButtonItem]];
// create title
[[self navigationItem] setTitle:#"Checklist"];
// create add guest button
UIBarButtonItem *bbi = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemAdd target:self action:#selector(pushAddTask)];
[[self navigationItem] setRightBarButtonItem:bbi];
}
- (void)pushAddTask
{
CLAddTaskViewController *advk = [[CLAddTaskViewController alloc] init];
[[self navigationController] pushViewController:advk animated:YES];
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
return [[[CLTaskStore sharedStore] allTasks] count];
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [checkList dequeueReusableCellWithIdentifier:CellIdentifier];
if (!cell) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
// put the tasks into the cell
[[cell textLabel] setText:[NSString stringWithFormat:#"%#", [[[CLTaskStore sharedStore] allTasks] objectAtIndex:[indexPath row]]]];
// put the checkbox into the cell's accessory view
UIButton *checkBox = [UIButton buttonWithType:UIButtonTypeCustom];
checkBox = [UIButton buttonWithType:UIButtonTypeCustom];
[checkBox setImage:[UIImage imageNamed:#"checkbox.png"] forState:UIControlStateNormal];
[checkBox setImage:[UIImage imageNamed:#"checkbox-checked.png"] forState:UIControlStateSelected];
checkBox.frame = CGRectMake(0, 0, 30, 30);
checkBox.userInteractionEnabled = YES;
[checkBox addTarget:self action:#selector(didCheckTask:) forControlEvents:UIControlEventTouchDown];
cell.accessoryView = checkBox;
}
return cell;
}
- (void)didCheckTask:(UIButton *)button
{
CGPoint hitPoint = [button convertPoint:CGPointZero toView:checkList];
hitIndex = [checkList indexPathForRowAtPoint:hitPoint];
task = [[[CLTaskStore sharedStore] allTasks] objectAtIndex:[hitIndex row]];
if (task.didComplete) {
task.didComplete = NO;
} else {
task.didComplete = YES;
}
NSInteger taskCount = [[[CLTaskStore sharedStore] allTasks] count];
for (int i = 0; i < taskCount; i++) {
NSLog(#"%#, status: %#", [[[CLTaskStore sharedStore] allTasks] objectAtIndex:i], [[[[CLTaskStore sharedStore] allTasks] objectAtIndex:i] didComplete]?#"YES":#"NO");
}
// toggle checkbox
button.selected = !button.selected;
}
- (void)setEditing:(BOOL)editing animated:(BOOL)animated
{
[super setEditing:editing animated:animated];
// set editing mode
if (editing) {
self.navigationItem.title = #"Edit Checklist";
[checkList setEditing:YES];
} else {
self.navigationItem.title = #"Checklist";
[checkList setEditing:NO];
}
}
- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle
forRowAtIndexPath:(NSIndexPath *)indexPath
{
// remove task
if (editingStyle == UITableViewCellEditingStyleDelete) {
// remove task from CLTaskStore
task = [[[CLTaskStore sharedStore] allTasks] objectAtIndex:[indexPath row]];
[[CLTaskStore sharedStore] removeTask:task];
// remove guest from table view
[checkList deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
// reload table view
//[checkList reloadData];
}
}
- (void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)sourceIndexPath toIndexPath:(NSIndexPath *)destinationIndexPath
{
[[CLTaskStore sharedStore] moveTaskAtIndex:[sourceIndexPath row] toIndex:[destinationIndexPath row]];
}
#end
CLAddTaskViewController.m
#import "CLAddTaskViewController.h"
#import "CLTaskFactory.h"
#import "CLTaskStore.h"
#implementation CLAddTaskViewController
- (void)viewDidLoad
{
[[self navigationItem] setTitle:#"Add Task"];
}
- (void)viewWillDisappear:(BOOL)animated
{
[super viewWillDisappear:animated];
// clear first responder
[[self view] endEditing:YES];
// create new task
CLTaskFactory *newTask = [[CLTaskFactory alloc] init];
[newTask setTaskName:[newTaskName text]];
// add new guest to RCGuestStore
[[CLTaskStore sharedStore] addTask:newTask];
}
#end
CLAddTaskFactory.m
#import "CLTaskFactory.h"
#implementation CLTaskFactory
#synthesize taskName;
- (void)setDidComplete:(BOOL)dc
{
didComplete = dc;
}
- (BOOL)didComplete
{
return didComplete;
}
- (NSString *)description
{
// override the description
NSString *descriptionString = [[NSString alloc] initWithFormat:#"%#", taskName];
return descriptionString;
}
#end
CLAddTaskStore.m
#import "CLTaskStore.h"
#import "CLTaskFactory.h"
#import "CLCheckListViewController.h"
#implementation CLTaskStore
+ (id)allocWithZone:(NSZone *)zone
{
return [self sharedStore];
}
+ (CLTaskStore *)sharedStore
{
static CLTaskStore *sharedStore = nil;
if (!sharedStore) {
sharedStore = [[super allocWithZone:nil] init];
}
return sharedStore;
}
- (id)init
{
self = [super init];
if (self) {
allTasks = [[NSMutableArray alloc] init];
}
return self;
}
- (NSMutableArray *)allTasks
{
return allTasks;
}
- (void)addTask:(CLTaskFactory *)task
{
[allTasks addObject:task];
NSLog(#"Task added: %#", task);
}
- (void)removeTask:(CLTaskFactory *)task
{
// remove the item for the deleted row from the store
[allTasks removeObjectIdenticalTo:task];
NSInteger taskCount = [allTasks count];
NSLog(#"Removed: %#, there are now %d remaining tasks, they are:", task, taskCount);
for (int i = 0; i < taskCount; i++) {
NSLog(#"%#, status: %#", [[[CLTaskStore sharedStore] allTasks] objectAtIndex:i], [[[[CLTaskStore sharedStore] allTasks] objectAtIndex:i] didComplete]?#"YES":#"NO");
}
}
- (void)moveTaskAtIndex:(int)from toIndex:(int)to
{
if (from == to) {
return;
}
CLTaskFactory *task = [allTasks objectAtIndex:from];
[allTasks removeObjectAtIndex:from];
[allTasks insertObject:task atIndex:to];
}
#end
Thanks for your help!

Answer 1

The table view seems to be reusing the dequeued cell
That's exactly what it does; it reuses cells whenever possible. If you had enough items to cause the table view to scroll, you'd also see the same problem.
In -tableView:cellForRowAtIndexPath: you must always set up the cell to display the correct content for the given row index, regardless of whether dequeueReusableCellWithIdentifier: returns a cell or not.
Basically:
If -dequeueReusableCellWithIdentifier: returns nil, create a new cell and add your checkbox button to it.
Then set the cell text and the button state on either this new cell or the cell returned from -dequeueReusableCellWithIdentifier:

Answer 2

Darren is correct. If you look at your code here:
if (!cell) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
// put the tasks into the cell
[[cell textLabel] setText:[NSString stringWithFormat:#"%#", [[[CLTaskStore sharedStore] allTasks] objectAtIndex:[indexPath row]]]];
// put the checkbox into the cell's accessory view
UIButton *checkBox = [UIButton buttonWithType:UIButtonTypeCustom];
checkBox = [UIButton buttonWithType:UIButtonTypeCustom];
[checkBox setImage:[UIImage imageNamed:#"checkbox.png"] forState:UIControlStateNormal];
[checkBox setImage:[UIImage imageNamed:#"checkbox-checked.png"] forState:UIControlStateSelected];
checkBox.frame = CGRectMake(0, 0, 30, 30);
checkBox.userInteractionEnabled = YES;
[checkBox addTarget:self action:#selector(didCheckTask:) forControlEvents:UIControlEventTouchDown];
cell.accessoryView = checkBox;
}
your only setting up the cell if(cell == nil)
Change your code to
if (!cell) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
}
// put the tasks into the cell
[[cell textLabel] setText:[NSString stringWithFormat:#"%#", [[[CLTaskStore sharedStore] allTasks] objectAtIndex:[indexPath row]]]];
// put the checkbox into the cell's accessory view
UIButton *checkBox = [UIButton buttonWithType:UIButtonTypeCustom];
checkBox = [UIButton buttonWithType:UIButtonTypeCustom];
[checkBox setImage:[UIImage imageNamed:#"checkbox.png"] forState:UIControlStateNormal];
[checkBox setImage:[UIImage imageNamed:#"checkbox-checked.png"] forState:UIControlStateSelected];
checkBox.frame = CGRectMake(0, 0, 30, 30);
checkBox.userInteractionEnabled = YES;
[checkBox addTarget:self action:#selector(didCheckTask:) forControlEvents:UIControlEventTouchDown];
cell.accessoryView = checkBox;