判断当前VC 是push还是present的

NSArray *viewcontrollers=self.navigationController.viewControllers;
    if (viewcontrollers.count>1) {
        if ([viewcontrollers objectAtIndex:viewcontrollers.count-1]==self) {
            //push方式
            [self.navigationController popViewControllerAnimated:YES];
        }
    }
    else{
        //present方式
        [self.navigationController dismissViewControllerAnimated:YES completion:nil];
    }