UIPickerView causing crash

Question

Whenever I try to select the UIPickerView in my App it crashes.

I have implemented all the delegate methods but receive this error:

2013-01-15 13:57:56.176 tracker[16142:c07] *** Assertion failure in -[UITableViewRowData rectForRow:inSection:], /SourceCache/UIKit_Sim/UIKit-2372/UITableViewRowData.m:1630
2013-01-15 13:57:56.177 tracker[16142:c07] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'request for rect at invalid index path (<NSIndexPath 0x918c700> 2 indexes [0, 0])'
*** First throw call stack:
(0x1c97012 0x10d4e7e 0x1c96e78 0xb6af35 0x2050c0 0xc892e 0x457fc6 0x457eba 0x7ba5d 0x7e03b 0x2e689a 0x2e59db 0x2e711f 0x2e9d6d 0x2e9cec 0x2e1a68 0x4efc2 0x4f4a3 0x2d3aa 0x1ecf8 0x1bf2df9 0x1bf2ad0 0x1c0cbf5 0x1c0c962 0x1c3dbb6 0x1c3cf44 0x1c3ce1b 0x1bf17e3 0x1bf1668 0x1c65c 0x29bd 0x28e5 0x1)
libc++abi.dylib: terminate called throwing an exception

Here are the implemented delegate methods:

- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)thePickerView {

    return 1;
}

- (NSInteger)pickerView:(UIPickerView *)thePickerView numberOfRowsInComponent:(NSInteger)component { 
    return [classes count];
}


- (NSString *)pickerView:(UIPickerView *)thePickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component {
    return [classes objectAtIndex:row];
}

- (void)pickerView:(UIPickerView *)thePickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component {

    NSLog(@"Selected Class: %@. Index of selected color: %i", [classes objectAtIndex:row], row);
}

'classes' is an NSMutableArray.

Here is how the view is wired up:

The view controlled is called MemberViewController.

My interface declaration contains the following:

@interface MemberViewController : UIViewController <UIPickerViewDataSource, UIPickerViewDelegate>

what am I doing wrong?

thankyou.

Answer 1

I had this problem in my previous app, I did a quick lookup and found this answer on Assertion failure on picker view

It is definitely a bug, unless memberPicker is declared as a UITableView object.

This code may fix it:

- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component
{
    if ([classes count] == 0)
        return 1;
     return [classes count];
}

What version of Xcode and iOS are you running on BTW?

Answer 2

I had a similar issue with my app. IIRC, the array that served as the data source had been declared weakly and it was being released such that the array count was 0 when didSelectRow was received (declaring it as strong resolved the issue). As noted by Rohan Kapur, there is a bug related to returning 0 from that method.

I would suggest logging the array count at the beginning of both numberOfRowsInComponent and didSelectRow to ensure that "classes" really contains what you expect.