C++。更改对象数据成员的数据成员

Question

这是我用来说明的简单代码。有一本 Book 的 Author 作为类内部的数据成员。 我想从测试程序修改作者的邮件，但 cppbook.getAuthor().setEmail("...") 不起作用。我尝试通过引用传递。 我找到了替代方案但并不令人满意。必须是一个简单的答案，我想我错过了什么。

class Author {
private:
    string name;
    string email;

public:
    Author(string name, string email) {
       this->name = name;
       this->email = email;
    }

    string getName() {
       return name;
    }

    string getEmail() {
       return email;
    }

    void setEmail(string email) {
       this->email = email;
    }

    void print() {
       cout << name << "-" << email << endl;
    }
};

---

class Book {
private:
   string name;
   Author author; // data member author is an instance of class Author

public:
    Book(string name, Author author)
          : name(name), author(author) {
    }

    string getName() {
       return name;
    }

    Author getAuthor() {
       return author;
    }

    void print() {
       cout << name << " - " << author.getEmail() << endl;
    }


    void setAuthorMail(string mail) {
       author.setEmail(mail);
    }
};

---

int main() {
   Author john("John", "john@gmail.com");
   john.print();  // John-john@gmail.com

   Book cppbook("C++ Introduction", john);
   cppbook.print();

   cppbook.getAuthor().setEmail("peter@gmail.com");
   cppbook.print(); //mail doesn't change: C++ Introduction - john@gmail.com
   cppbook.setAuthorMail("andrew@gmail.com");
   cppbook.print(); //mail changes: C++ Introduction - andrew@gmail.com
}

Live Example

Answer 1

I want to modify the mail from the Author from the test program, but cppbook.getAuthor().setEmail("...") doesn't work.

Author getAuthor();应该是 Author& getAuthor();如果你想更改关联到 Book 的内部对象.

否则，您只是在更改 Author 的临时拷贝实例。