ios7 tableview被navigationbar挡住

NSComparisonResult order = [[UIDevice currentDevice].systemVersion compare: @"7.0" options: NSNumericSearch];
if (order == NSOrderedSame || order == NSOrderedDescending)
{
    // OS version >= 7.0
    self.edgesForExtendedLayout = UIRectEdgeNone;
}

或者

        if (ios_version>=7.0) {
            self.edgesForExtendedLayout=UIRectEdgeNone;
        }