Question

I ran into this issue twice now, and am curious to know if there is a correct way of getting the following example to work. I know there are other ways /workarounds for doing the same thing but I am wondering why the compiler doesn’t recognise my casting and if I am missing something obvious here.

Suppose I have two table views with different style header views that I need to provide. SectionHeaderViewA is a UIView subclass with a custom property textLabelA, SectionHeaderViewB is also a UIView subclass with a custom property textLabelB.

In the method:

- (UIView*)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section
{
    id headerView;
    if (tableView.tag == TAG_A)
    {
        headerView = (SectionHeaderViewA*)[[SectionHeaderViewA alloc] init];
        headerView.textLabelA = ... // I am unable to access the custom property here even after casting (SectionHeaderViewA*) above.
    } else if (tableView.tag == TAG_B) {
        headerView = (SectionHeaderViewB*)[[SectionHeaderViewB alloc] init];
        headerView.textLabelB = ... // Same as above, even after casting the custom property is not recognised
    }
    return headerView;
}

Even after casting (SectionHeaderViewA*) and (SectionHeaderViewB*) to my headerView ivar, I am still unable to access their respective custom properties. It’s like the compiler is still seeing headerView as an unknown / id type but why?

Answer 1

The cast is not in the correct place. Cast headerView before sending the appropriate textLabel A or B message.

id headerView;
if (tableView.tag == TAG_A)  
{  
    headerView = [[SectionHeaderViewA alloc] init];
    ((SectionHeaderViewA*)headerView).textLabelA = ... // I am unable to access the custom property here even after casting (SectionHeaderViewA*) above.
} else if (tableView.tag == TAG_B) {
    headerView = [[SectionHeaderViewB alloc] init];
    ((SectionHeaderViewB*)headerView).textLabelB = ... // Same as above, even after casting the custom property is not recognized
}
return headerView;  

Once you move the cast, you will be able to send the correct message.