Code working on iPhone 5, not on iPod touch 4 - iphone

Question

I'm testing my application on different devices. The app works fine on my iPhone 5, however, when I test it on my iPod touch 4g, I get this eror:
*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** [__NSArrayMinsertObject:atIndex:]: object cannot be nil'
*** First throw call stack:
(0x33f252a3 0x3bba397f 0x33e6f8d9 0x51e25 0x35e180c5 0x35e1814d 0x35e180c5 0x35e18077 0x35e18055 0x35e1790b 0x35e17e01 0x35d405f1 0x35d2d801 0x35d2d11b 0x37a1f5a3 0x37a1f1d3 0x33efa173 0x33efa117 0x33ef8f99 0x33e6bebd 0x33e6bd49 0x37a1e2eb 0x35d81301 0x4fc8d 0x3bfdab20)
libc++abi.dylib: terminate called throwing an exception
The code that's crashing is this one:
/********/
NSMutableArray *titulosCampoTextArray = [[NSMutableArray alloc] init];
for (int i = 0; i < campos.count; i++) {
SignupCell *cell = (SignupCell*)[self.tableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:i inSection:0]];
[titulosCampoTextArray addObject:cell.textField.text];
}
/********/
I'm using custom prototype cells (SignupCell.h), on a UITableView inside a UIView.
Can't find the error, or how to fix it.
EDIT: Both devices are running iOS 6.1.3, and I'm using Xcode 4.6.1.

Answer 1

UITableView's -cellForRowAtIndexPath: method returns nil if the cell isn't visible on screen when you call it.
My guess is that on the iPhone 5 your table can display all rows at once, while on the shorter iPod touch, the last one or two cells aren't visible and -cellForRowAtIndexPath: thus returns nil, which makes your app crash.
You shouldn't rely on -cellForRowAtIndexPath to request model data! Your view controller is responsible for the data, not the table view.
Use the same way to access the model data like you do for setting the table view cells' text in the -tableView:cellForRowAtIndexPath: data source method of your view controller.

Answer 2

Just do this:
NSMutableArray *titulosCampoTextArray = [[NSMutableArray alloc] init];
for (int i = 0; i < campos.count; i++) {
SignupCell *cell = (SignupCell*)[self.tableView
cellForRowAtIndexPath:[NSIndexPath indexPathForRow:i inSection:0]];
if (cell.textField.text) {
[titulosCampoTextArray addObject:cell.textField.text];
}
}
I don't know why you apparently can add nil on an iPhone 5 but not on an iPod. It may be that for some other reason you just never happen to have a nil value for cell.textField.text when your app is running on the iPhone 5.