在视图类View中通过添加菜单项函数调用Doc类中的成员函数来实现具体的添加硬币、减少硬币操作。此时需要考虑各菜单相应函数能够获取文档类对象,见程序-By adding a member function menu items function calls in the Doc class to achieve add coins, concrete reduce coin operation in the view class in View. At this time the need to