Tae Tae - 4 months ago 15
Objective-C Question

Return a custom cell from cellForRowAtIndexPath:

I ran into a trouble and I'm looking for help.

I need to save a identifier in a cell, so I did a subclass
of UITableViewCell and added to it the identifier property. In my view
controller I create the cells as follow:

- (SidebarCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
UITableViewCell* tableViewCell = [super tableView:tableView cellForRowAtIndexPath:indexPath];
SidebarCell * cell = (SidebarCell *)tableViewCell;
Category *category = [categoryDataController.categories objectAtIndex:indexPath.row];
cell.textLabel.text = category.name;

if (category.checked == 1) {
cell.accessoryType = UITableViewCellAccessoryCheckmark;
} else {
cell.accessoryType = UITableViewCellAccessoryNone;
}

return cell;
}


The problem is that when I select one of the cells, the method
cellForRowAtIndexPath: returns an UTableViewCell object instead
of a SidebarCell, so I don't have access to the identifier property:

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
[tableView deselectRowAtIndexPath:[tableView indexPathForSelectedRow] animated:NO];
SidebarCell *cell = (SidebarCell *)[tableView cellForRowAtIndexPath:indexPath]; // Trying to cast from UITableViewCell to SidebarCell

if (cell.accessoryType == UITableViewCellAccessoryNone) {
cell.accessoryType = UITableViewCellAccessoryCheckmark;
[CategoryDataController updateRow:cell.identifier status:1]; // Here the app crashes
} else if (cell.accessoryType == UITableViewCellAccessoryCheckmark) {
cell.accessoryType = UITableViewCellAccessoryNone;
[CategoryDataController updateRow:cell.identifier status:0];
}
}


is there a way for cellForRowAtIndexPath: to return an Sidebarcell object?

Thanks beforehand.

Edit

The SidebarCell.h

#import <UIKit/UIKit.h>

@interface SidebarCell : UITableViewCell

@property (nonatomic) NSInteger identifier;

@end


SidebarCell.m:

#import "SidebarCell.h"

@implementation SidebarCell

@synthesize identifier;

- (id)initWithStyle:(UITableViewCellStyle)style reuseIdentifier:(NSString *)reuseIdentifier
{
self = [super initWithStyle:style reuseIdentifier:reuseIdentifier];
return self;
}

- (void)setSelected:(BOOL)selected animated:(BOOL)animated
{
[super setSelected:selected animated:animated];

// Configure the view for the selected state
}

@end


The error:

2012-04-24 09:21:08.543 Dongo[2993:11603] -[UITableViewCell identifier]: unrecognized selector sent to instance 0x6d87d50
2012-04-24 09:21:08.571 Dongo[2993:11603] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[UITableViewCell identifier]: unrecognized selector sent to instance 0x6d87d50'
*** First throw call stack:
(0x14b1052 0x1a65d0a 0x14b2ced 0x1417f00 0x1417ce2 0x116bc 0x48e71d 0x48e952 0xd1686d 0x1485966 0x1485407 0x13e87c0 0x13e7db4 0x13e7ccb 0x239d879 0x239d93e 0x3fea9b 0x2e85 0x2715 0x1)
terminate called throwing an exception(lldb)

Answer

You should leave the tableView:cellForRowAtIndexPath: method signature intact: it should return (UITableViewCell *) and not your custom cell class. Since your SidebarCell is a subclass of UITableViewCell, it should all "just work". No need to call super or any of that:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    SidebarCell *cell = [tableView dequeueReusableCellWithIdentifier:@"CellIdentifier"];
    if (cell == nil) {
        cell = [[SidebarCell alloc] initWithStyle:UITableViewCellStyleDefault
                                  reuseIdentifier:@"CellIdentifier@"];
    }
    // ... set up the cell here ...
    return cell;
}

In other methods, the cast should work just as you have it:

SidebarCell *cell = (SidebarCell *)[tableView cellForRowAtIndexPath:indexPath];