why am I getting error "[UIViewController tableView:numberOfRowsInSection:]: unrecognized selector sent to instance 0x4e38c50'"?

Question

I made a TabBarApplication, and made 3 controllers, 1 of them is inheriting UITableViewController , I am putting number of sections are "return 1" and number of rows in section as "return 2",

I am getting the following problem, why?

[UIViewController tableView:numberOfRowsInSection:]: unrecognized selector sent to instance 0x4e38c50'"

#import <UIKit/UIKit.h>


@interface List : UITableViewController {

}

@end

and .m file is

    #import "List.h"


    @implementation List


    #pragma mark -
    #pragma mark View lifecycle

/*
- (void)viewDidLoad {
    [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 10;
}


// 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...

    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.
        [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
    }   
    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

Pls check the datasource of the tableView. I think its not properly set-up. If the dataSource is not setup properly it can cause issues

Answer 2

This happens when you set a table view delegate/datasource that does not implement the methods declared on the delegate/datasource protocol.

Without looking at the code I cant tell you exactly what you are doing wrong but if you create the controller using an xcode template just make usre you are initializing it as a UITableViewController and nota general UIVIewController.

If you post your code I can help you work out whats wrong, but as I said, this error happens when the tableview delegate does not implement the tableView:numberOfRowsInSection: method; if you say you are implementing this method then the tableview is not assigned linked to that controller class..

Answer 3

Well I do this mistake all the Time. Under Outlets, make sure you drag the outlet to the "ViewController" and not the "View". I normally use the "Document Outline" for connecting just to make sure. Hope this helps.