C++ 用智能指针这样包装 this 指针是否可行

#include <iostream>
#include <memory>

using namespace std;

class A;
class B
{
public:
    B(shared_ptr<A> a)
    {
        pa = a;
        cout << "B 构造..." << endl;
    }
    ~B()
    {
        cout << "B 析构..." << endl;
    }
    shared_ptr<A> pa;

public:
    void Hello()
    {
        cout << "hello I am B Obj." << endl;
    }
};

class C
{
public:
    C(shared_ptr<A> a)
    {
        pa = a;
        cout << "C 构造..." << endl;
    }
    ~C()
    {
        cout << "C 析构..." << endl;
    }
    shared_ptr<A> pa;

public:
    void Hello()
    {
        cout << "hello I am C Obj." << endl;
    }
};

class A
{
public:
    A()
    {
        cout << "A 构造..." << endl;
        self = shared_ptr<A>(this, [](A* a) { cout << "跳过 delete." << endl; });
        pb = make_shared<B>(self);
        pc = make_shared<C>(self);
    }
    ~A()
    {
        cout << "A 析构..." << endl;
    }
    shared_ptr<B> pb;
    shared_ptr<C> pc;
private:
    shared_ptr<A> self;
public:
    void Hello()
    {
        cout << "hello I am A Obj." << endl;
    }
};

int main()
{
    auto a = make_shared<A>();

    a->pb->Hello();
    a->pc->Hello();
    a->pb->pa->Hello();
    a->pc->pa->Hello();

    system("pause");
    return 0;
}

输出：

A 构造...
B 构造...
C 构造...
hello I am B Obj.
hello I am C Obj.
hello I am A Obj.
hello I am A Obj.
请按任意键继续. . .
A 析构...
C 析构...
B 析构...
跳过 delete.

.exe (进程 1940)已退出，代码为 0。
要在调试停止时自动关闭控制台，请启用“工具”->“选项”->“调试”->“调试停止时自动关闭控制台”。
按任意键关闭此窗口. . .

---

多文件拆分

A.h

#pragma once

#include <memory>
#include "B.h"
#include "C.h"

class A
{
public:
    A();
    ~A();
    std::shared_ptr<B> pb;
    std::shared_ptr<C> pc;
    void Hello();
private:
    std::shared_ptr<A> self;
};

A.cpp

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

A::A()
{
    std::cout << "A 构造..." << std::endl;
    self = std::shared_ptr<A>(this, [](A* a) {  std::cout << "跳过 delete." << std::endl; });
    pb = std::make_shared<B>(self);
    pc = std::make_shared<C>(self);
}

A::~A()
{
    std::cout << "A 析构..." << std::endl;
}

void A::Hello()
{
    std::cout << "hello I am A Obj." << std::endl;
}

B.h

#pragma once
#include <memory>

class A;

class B
{
public:
    B(std::shared_ptr<A> a);
    ~B();
    std::shared_ptr<A> pa;
    void Hello();
};

B.cpp

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

B::B(std::shared_ptr<A> a)
{
    pa = a;
    std::cout << "B 构造..." << std::endl;
}

B::~B()
{
    std::cout << "B 析构..." << std::endl;
}

void B::Hello()
{
    std::cout << "hello I am B Obj." << std::endl;
}

C.h

#pragma once
#include <memory>

class A;
class C
{
public:
    C(std::shared_ptr<A> a);
    ~C();
    std::shared_ptr<A> pa;
    void Hello();
};

C.cpp

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

C::C(std::shared_ptr<A> a)
{
    pa = a;
    std::cout << "C 构造..." << std::endl;
}

C::~C()
{
    std::cout << "C 析构..." << std::endl;
}

void C::Hello()
{
    std::cout << "hello I am C Obj." << std::endl;
}

main.cpp

#include <memory>
#include "A.h"

int main()
{
    auto a = std::make_shared<A>();

    a->pb->Hello();
    a->pc->Hello();
    a->pb->pa->Hello();
    a->pc->pa->Hello();

    system("pause");
    return 0;
}

输出：

A 构造...
B 构造...
C 构造...
hello I am B Obj.
hello I am C Obj.
hello I am A Obj.
hello I am A Obj.
请按任意键继续. . .
A 析构...
C 析构...
B 析构...
跳过 delete.

.exe (进程 15216)已退出，代码为 0。
要在调试停止时自动关闭控制台，请启用“工具”->“选项”->“调试”->“调试停止时自动关闭控制台”。
按任意键关闭此窗口. . .