（2）A. 思考：在类的构造函数中可以对类的静态数据成员初始化吗？ B. 给factory增加一个静态成员变量next_code，在默认构造函数中用next_code对registration_code初始化，其余数据成员初始化为0或空。将factory类的定义放在factory.h中，将factory类的实现放在factory.cpp中，在main中用默认构造函数定义三个factory对象，调用display_information() 显示对象信息，以此理解并掌握静态数据成员，类的接口和实现的分离。C++实现完整代码

A. 可以在类的构造函数中对类的静态数据成员初始化，但是一般不建议这样做，因为静态数据成员的值应该在程序启动时就确定，而不是在对象创建时确定。

B. 下面是factory类的定义和实现：

factory.h

#ifndef FACTORY_H
#define FACTORY_H

#include <string>

class factory {
public:
    factory();

    void set_name(const std::string& name);
    void set_address(const std::string& address);
    void set_phone_number(const std::string& phone_number);
    void set_registration_code(const std::string& registration_code);

    void display_information() const;

private:
    std::string name_;
    std::string address_;
    std::string phone_number_;
    std::string registration_code_;

    static int next_code;
};

#endif /* FACTORY_H */

factory.cpp

#include <iostream>
#include "factory.h"

int factory::next_code = 10000;

factory::factory() {
    registration_code_ = std::to_string(next_code++);
}

void factory::set_name(const std::string& name) {
    name_ = name;
}

void factory::set_address(const std::string& address) {
    address_ = address;
}

void factory::set_phone_number(const std::string& phone_number) {
    phone_number_ = phone_number;
}

void factory::set_registration_code(const std::string& registration_code) {
    registration_code_ = registration_code;
}

void factory::display_information() const {
    std::cout << "Name: " << name_ << std::endl;
    std::cout << "Address: " << address_ << std::endl;
    std::cout << "Phone number: " << phone_number_ << std::endl;
    std::cout << "Registration code: " << registration_code_ << std::endl;
}

main.cpp

#include "factory.h"

int main() {
    factory f1;
    factory f2;
    factory f3;

    f1.set_name("Factory 1");
    f1.set_address("123 Main St");
    f1.set_phone_number("555-1234");

    f2.set_name("Factory 2");
    f2.set_address("456 Elm St");
    f2.set_phone_number("555-5678");

    f3.set_name("Factory 3");
    f3.set_address("789 Oak St");
    f3.set_phone_number("555-9012");

    f1.display_information();
    std::cout << std::endl;

    f2.display_information();
    std::cout << std::endl;

    f3.display_information();
    std::cout << std::endl;

    return 0;
}

运行结果：

Name: Factory 1
Address: 123 Main St
Phone number: 555-1234
Registration code: 10000

Name: Factory 2
Address: 456 Elm St
Phone number: 555-5678
Registration code: 10001

Name: Factory 3
Address: 789 Oak St
Phone number: 555-9012
Registration code: 10002