How to delete a row from UITableView

Question

I'm trying to delete a row from my table view and so far have been unsuccessful. I keep getting this error:

"Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Invalid update: invalid number of rows in section 0. The number of rows contained in an existing section after the update (5) must be equal to the number of rows contained in that section before the update (5), plus or minus the number of rows inserted or deleted from that section (0 inserted, 1 deleted).'" The array which i use to populate the table view is declared in that class, also i get my objects for my array from an sqlite db.

The code that i used to try deleting rows is as follows.

- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath {

if (editingStyle == UITableViewCellEditingStyleDelete) {
    // Delete the row from the data source

    [categoryArray objectAtIndex:indexPath.row];
    [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:YES];

}   
else if (editingStyle == UITableViewCellEditingStyleInsert) {
    // Create a new instance of the appropriate class, insert it into the array, and add a new row to the table view
}   
}

Now for the questions i hope to get answered:

-How can i delete rows properly?

-Will i face deleting the row if its the only one left in the tableView?

-Can i change the tableView that is used in the method to be the UITableView i declared in my .h file?

Many Thanks.

---

Edit

-Full .m code

#import "DeleteCategoryTableView.h"
#import "KeyCryptAppAppDelegate.h"


@implementation DeleteCategoryTableView
@synthesize categoryArray;

#pragma mark -
#pragma mark Initialization

-(void) initializeCategoryArray {

sqlite3 *db= [KeyCryptAppAppDelegate getNewDBConnection];
KeyCryptAppAppDelegate *appDelegate = (KeyCryptAppAppDelegate *)[[UIApplication sharedApplication] delegate];

const char *sql = [[NSString stringWithFormat:(@"Select Category from Categories;")]cString];


sqlite3_stmt *compiledStatement;



if (sqlite3_prepare_v2(db, sql, -1, &compiledStatement, NULL)==SQLITE_OK)
{
    while(sqlite3_step(compiledStatement) == SQLITE_ROW)
        [categoryArray addObject:[NSString stringWithUTF8String:(char*) sqlite3_column_text(compiledStatement, 0)]];

}
else {
    NSAssert1(0,@"Error preparing statement", sqlite3_errmsg(db));
}
sqlite3_finalize(compiledStatement);
}
/*
- (id)initWithStyle:(UITableViewStyle)style {
// Override initWithStyle: if you create the controller programmatically and want to perform customization that is not appropriate for viewDidLoad.
if ((self = [super initWithStyle:style])) {
}
return self;
}
*/
#pragma mark -
#pragma mark View lifecycle
- (void)viewDidLoad {
self.title = NSLocalizedString(@"Delete Categories",@"Delete your Categories");
categoryArray = [[NSMutableArray alloc]init];
[self initializeCategoryArray];
[super viewDidLoad];

// Uncomment the following line to display an Edit button in the navigation bar for this view controller.
self.navigationItem.rightBarButtonItem = self.editButtonItem;
}
/*
- (void)viewWillAppear:(BOOL)animated {
[super viewWillAppear:animated];
}
*/
/*
- (void)viewDidAppear:(BOOL)animated {
[super viewDidAppear:animated];
}
*/
/*
- (void)viewWillDisappear:(BOOL)animated {
[super viewWillDisappear:animated];
}
*/
/*
- (void)viewDidDisappear:(BOOL)animated {
[super viewDidDisappear:animated];
}
*/
/*
// Override to allow orientations other than the default portrait orientation.
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {
// Return YES for supported orientations
return (interfaceOrientation == UIInterfaceOrientationPortrait);
}
*/


#pragma mark -
#pragma mark Table view data source

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
// Return the number of sections.
return 1;
}


- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section    {
// Return the number of rows in the section.
return [self.categoryArray count];
}


// Customize the appearance of table view cells.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {

static NSString *CellIdentifier = @"Cell";

UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
    cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
}

// Configure the cell...
NSUInteger row = [indexPath row];
cell.text = [categoryArray objectAtIndex:row];
return cell;
}
/*
// Override to support conditional editing of the table view.
- (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath {
// Return NO if you do not want the specified item to be editable.
return YES;
}
*/
// Override to support editing the table view.
- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath {

if (editingStyle == UITableViewCellEditingStyleDelete) {
    // Delete the row from the data source

    [categoryArray removeObjectAtIndex:indexPath.row];
    [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:YES];
    [deleteCategoryTable reloadData];

    NSString *selectedCategory = [categoryArray objectAtIndex:indexPath.row];

    sqlite3 *db= [KeyCryptAppAppDelegate getNewDBConnection];
    KeyCryptAppAppDelegate *appDelegate = (KeyCryptAppAppDelegate *)[[UIApplication sharedApplication] delegate];
    const char *sql = [[NSString stringWithFormat:@"Delete from Categories where Category = '%@';", selectedCategory]cString];

    sqlite3_stmt *compiledStatement;


    if (sqlite3_prepare_v2(db, sql, -1, &compiledStatement, NULL)==SQLITE_OK)
    {
        sqlite3_exec(db,sql,NULL,NULL,NULL);

    }
    else {
        NSAssert1(0,@"Error preparing statement", sqlite3_errmsg(db));
    }
    sqlite3_finalize(compiledStatement);
}



else if (editingStyle == UITableViewCellEditingStyleInsert) {
    // Create a new instance of the appropriate class, insert it into the array, and add a new row to the table view
}   
}
/*
// Override to support rearranging the table view.
- (void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)fromIndexPath toIndexPath:(NSIndexPath *)toIndexPath {
}
*/
/*
// Override to support conditional rearranging of the table view.
- (BOOL)tableView:(UITableView *)tableView canMoveRowAtIndexPath:(NSIndexPath *)indexPath {
// Return NO if you do not want the item to be re-orderable.
return YES;
}
*/
#pragma mark -
#pragma mark Table view delegate
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
// Navigation logic may go here. Create and push another view controller.
/*
 <#DetailViewController#> *detailViewController = [[<#DetailViewController#> alloc] initWithNibName:@"<#Nib name#>" bundle:nil];
 // ...
 // Pass the selected object to the new view controller.
 [self.navigationController pushViewController:detailViewController animated:YES];
 [detailViewController release];
 */
}
#pragma mark -
#pragma mark Memory management

- (void)didReceiveMemoryWarning {
// Releases the view if it doesn't have a superview.
[super didReceiveMemoryWarning];

// Relinquish ownership any cached data, images, etc that aren't in use.
}

- (void)viewDidUnload {
// Relinquish ownership of anything that can be recreated in viewDidLoad or on demand.
// For example: self.myOutlet = nil;
}


- (void)dealloc {
[super dealloc];
}


@end

Answer 1

This is ALL you need to do. It comes down to implement one method fairly well.

Swift 2

func tableView(tableView: UITableView, commitEditingStyle editingStyle: UITableViewCellEditingStyle, forRowAtIndexPath indexPath: NSIndexPath) {
    if editingStyle == .Delete {

        //1. remove data from model
        data.removeAtIndex(indexPath.row) 

        //2. remove row from view
        tableView.deleteRowsAtIndexPaths([indexPath], withRowAnimation: .Fade) 

        //3. custom method to update your view after removing
        updateView() 
    }
}

Swift 3

func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath) {
    if editingStyle == .delete {

        //1. remove data from model
        data.remove(at: indexPath.row)

        //2. remove row from view
        tableView.deleteRows(at: [indexPath as IndexPath], with: .fade)

        //3. custom method to update your view after removing
        updateView()
    }
}

Answer 2

1) The problem with deleting is

[categoryArray removeObjectAtIndex:indexPath.row];

Remove it from db too.

Once you delete the row, reload the tableView using [tableView reloadData]

2) There is no problem if it is the only one item

Edit:

This is the problem

[categoryArray removeObjectAtIndex:indexPath.row];
NSString *selectedCategory = [categoryArray objectAtIndex:indexPath.row];

You have deleted the value at indexPath.row from array after that accessing the value at same indexPath.row, obviously it will delete the next value only.. :)

So put that

NSString *selectedCategory = [categoryArray objectAtIndex:indexPath.row]

line before [categoryArray removeObjectAtIndex:indexPath.row];

Answer 3

Read what the problem from the console is.

You have a method numberOfRowsInSection... lets say its set to return 5;.

When you delete a row from the table view you also need to update this method... so its looking for you to return 4; from that method.

Basically you need to make sure that the number of row in your table view is ONE LESS than before you deleted your row.

Answer 4

for this purpose dont try to delete the row try to delete from array or data source(in case array is preparing from database) then try to reload array by simply call the database function.

then

[table reloadData].

this is the correct practice.

Answer 5

Your code is fine, expect that withRowAnimation: doesn't expect a BOOL but a UITableViewRowAnimation member. Eg. UITableViewRowAnimationRight to let it slide out to the right side of the table.

Also: You just fetch the object from the array, you have to delete it! If its an mutable array, you can use [categoryArray removeObjectAtIndex:indexpath.row]