在继承类中调用方法报错

有两个类A和B。
在A类中：
@interface A : B

在B类中，得到如下代码：

self.navigationItem.rightBarButtonItem = [UIBarButtonItem barItemWithImage:[UIImage imageNamed:@"Add-button-normal"]
                                                          highlightedImage:[UIImage imageNamed:@"Add-button-active"]
                                                                    target:self
                                                                    action:@selector(showPopoverUI:)];

然后我在A类中访问条目，用下面代码之后没有实现：

self.navigationItem.rightBarButtonItem = [UIBarButtonItem barItemWithImage:[UIImage imageNamed:@"Add-button-normal"]
                                                          highlightedImage:[UIImage imageNamed:@"Add-button-active"]
                                                                    target:self.parentViewController
                                                                    action:@selector(showPopoverUI:)];

然后系统给我错误：

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '+[B showPopoverUI:]: unrecognized selector sent to class 0x226308'