使用NSComboBox和controlTextDidEndEditing

Question

我有一个NSComboBox，我试图让它成为当用户选择一个名字时，其他信息（费率，费率类型和国籍）会自动输入。它有时会起作用，但在其他时候会导致错误。

此代码：

public class Output 
{
    string aProperty;
    int Count;

    public override string ToString()
    {
        return string.Format("{0}: {1}", aProperty, Count);//Or whatever you want
    }
}

导致此错误：

- (void)controlTextDidEndEditing:(NSNotification *)aNotification{

    NSInteger index = [_nameBox indexOfItemWithObjectValue:[_nameBox stringValue]];
    _lblRate.stringValue =[[contents objectAtIndex:index] objectForKey:@"Rate"];

    NSInteger rateType =[[[contents objectAtIndex:index] objectForKey:@"RateType"] integerValue];
    [_rateTypeSwitcher setSelected:YES forSegment:rateType];

    [_nationalityMenu selectItemWithTitle:[[contents objectAtIndex:index] objectForKey:@"Nationality"]];

}