C++打印结构体的方法

通常在 C++ 语言中，我们无法直接对结构体打印，但是可以通过某种方式来打印结构体。

使用友元函数打印

class my_class
{
public:
    int i;
    std::string s;

    friend std::ostream& operator<<(std::ostream& os, const  my_class& obj)
    {
        return os << "i: " << obj.i << " s: " << obj.s;
    }
};

int main()
{
    my_class obj;
    obj.i = 1;
    obj.s = "hello";
    std::cout << obj << std::endl;
    return 0;
}

使用宏定义简化定义流程

#define FRIEND_STREAM_1(type, x1)                                           \
    friend std::ostream& operator<<(std::ostream& os, const type& type_obj) \
    {                                                                       \
        os << #type << ": this(" << &type_obj << "), ";                     \
        os << #x1 << "(" << type_obj.x1 << ")";                             \
        return os;                                                          \
    }

#define FRIEND_STREAM_2(type, x1, x2)                                       \
    friend std::ostream& operator<<(std::ostream& os, const type& type_obj) \
    {                                                                       \
        os << #type << ": this(" << &type_obj << "), ";                     \
        os << #x1 << "(" << type_obj.x1 << "), ";                           \
        os << #x2 << "(" << type_obj.x2 << ") ";                            \
        return os;                                                          \
    }

#define FRIEND_STREAM_3(type, x1, x2, x3)                                   \
    friend std::ostream& operator<<(std::ostream& os, const type& type_obj) \
    {                                                                       \
        os << #type << ": this(" << &type_obj << "), ";                     \
        os << #x1 << "(" << type_obj.x1 << "), ";                           \
        os << #x2 << "(" << type_obj.x2 << "), ";                           \
        os << #x3 << "(" << type_obj.x3 << ") ";                            \
        return os;                                                          \
    }

class my_class
{
public:
    int i;
    std::string s;

    FRIEND_STREAM_2(my_class, i, s);
};