David is right!
I don't agree with you saying
In my table, I don't know, in advance, which row will include which custom cell; I only get this data in cellForRowAtIndexPath where I check in the data array which case I need to represent for a specific row.
in heightForRowAtIndexPath you can access you datasource the same way you do it in cellForRowAtIndexPath:
-(CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath {
CGFloat bigCellHeight = 80.0;
CGFloar regularCellHeight = 44.0;
MyDataObject *object = [myArray objectAtIndex: indexPath.row];
if ([object anyConditionToChoseBigCell]) {
return bigCellHeight;
}
return regularCellHeight;
}