错误 - 无法在C++中调用没有对象的成员函数

Question

我收到编译错误

cannot call member function ‘bool GMLwriter::write(const char*, MyList<User*>&, std::vector<std::basic_string<char> >)’ without object

当我尝试编译

 class GMLwriter{
    public:
    bool write(const char *fn, MyList<User*>& my_vec, vector<string>edges);
};

功能被后面定义和被叫main用

GMLwriter::write(argv[3], Users, edges);

之前声明了用户MyList<User*> Users;(MyList是List ADT,我有一个User类),并且声明了edgevector<string>edges

什么object是这个错误指？

Answer 1

GMLwriter::write不是GMLwriter的静态函数,需要通过对象调用它.例如:

GMLwriter gml_writer;   
gml_writer.write(argv[3], Users, edges);

如果GMLwriter::write不依赖于任何GMLwriter状态(访问任何成员GMLwriter),则可以使其成为静态成员函数.然后你可以直接调用它而不需要对象:

class GMLwriter
{
public:
   static bool write(const char *fn, MyList<User*>& my_vec, vector<string>edges);
   ^^^^
};

然后你可以打电话:

GMLwriter::write(argv[3], Users, edges);