Passed UIButton parameter nil in target method - iphone

Question

I'm trying to properly set the target of a UIButton touched event in a subclass of UITableCell (designed in IB) that will delete that cell. However, when ran in the simulator, I get the following error:
* Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '* - [__NSPlaceholderArray
initWithObjects:count:]: attempt to insert nil object from objects[0]'
It gets to the method fine, but it always crashes right after the NSArray arrayWithObject line. It seems that the cause of this is because the button passed in to the target method is always nil.
I'm assuming this is a memory issue, but I'm quite baffled as to how to fix it. Do I just need to create the cell entirely programmatically to get this to work, or is there an easy way to somehow specify the target of the buttons action as the main ViewController from Interface Builder?
Here's where the cells are created in the view controller:
-(UITableViewCell *)tableView:(UITableView *)tableView
cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
if(tableView==songList){
static NSString *SimpleTableIdentifier = #"SimpleTableIdentifier";
SongCell *cell = (SongCell *)[tableView dequeueReusableCellWithIdentifier:SimpleTableIdentifier];
if(cell == nil) {
NSArray *nib = [[NSBundle mainBundle] loadNibNamed:#"SongCell" owner:self options:nil];
cell = [nib objectAtIndex:0];
[cell.addButton addTarget:self action:#selector(addToPlaylist:) forControlEvents:UIControlEventTouchUpInside];
}
NSUInteger row = [indexPath row];
cell.songname.text = #"test";//[songListData objectAtIndex:row];
return cell;
}
return nil;
}
And here's the target method:
-(void)addToPlaylist:(id)button{
SongCell *song = (SongCell *)[(UIButton *)button superview];
NSIndexPath *indexPath = [self.songList indexPathForCell:song];
NSArray *rowToMove = [NSArray arrayWithObject:indexPath];
[self.songList beginUpdates];
[self.songList deleteRowsAtIndexPaths:rowToMove withRowAnimation:UITableViewRowAnimationFade];
[self.songList endUpdates];
}
Any help you can offer would be greatly appreciated.

Answer 1

The error is b/c indexPath must be nil. There are a number of suspect things in your code sample. What is your implementation of SongCell? When you add subviews to a cell you should add them to the cell's contentView vs directly to the cell. It is likley that [button superview] is not returning the cell and therefore the next line is returning nil for the indexPath.
A few other thoughts:
It looks like you only need the row number when the button is pressed. You could store the rowIndex + 1 in the button tag property and then retrieve it - 1 in addToPlaylist:. You need to +/- b/c the tag property should be > 0. Alternatively use a UIButton subclass that has a property to store your indexPath.
If you're going to delete a row via deleteRowsAtIndexPaths:withRowAnimation: you need to first delete the same row from the data source to maintain the integrity of the table.
If you are only doing a single deletion, you don't need beginUpdates/endUpdates.