TableView滚动道底部安全的处理方案

- (void)scrollToBottom{
    if ([self.tableView numberOfSections] == 0 || self.tableView.decelerating || self.tableView.tracking) {
        return;
    }
    NSIndexPath *lastCell = [NSIndexPath indexPathForItem:([self.tableView numberOfRowsInSection:0] - 1) inSection:0];
    [self scrollToIndexPath:lastCell animated:YES];
}
- (void)scrollToIndexPath:(NSIndexPath *)indexPath animated:(BOOL)animated
{
    
    if ([self.tableView numberOfSections] <= indexPath.section) {
        return;
    }
    NSInteger numberOfItems = [self.tableView numberOfRowsInSection:indexPath.section];
    if (numberOfItems == 0) {
        return;
    }
    NSInteger item = MAX(MIN(indexPath.item, numberOfItems - 1), 0);
    indexPath = [NSIndexPath indexPathForItem:item inSection:0];
    [self.tableView scrollToRowAtIndexPath:indexPath atScrollPosition:UITableViewScrollPositionTop animated:animated];
}