无法访问另一个函数c++类中的成员

class A {
public:
    void somePublicFunction() {
        B b;
        b.someMemberFunction();
    }
    
    friend class B;
};

class B {
public:
    void someMemberFunction() {
        A a;
        // 可以访问A类中的私有成员
        a.somePrivateMember = 10;
    }
};

int main() {
    A a;
    a.somePublicFunction();
    return 0;
}

class A {
private:
    int somePrivateMember;

public:
    int getSomePrivateMember() const {
        return somePrivateMember;
    }

    void setSomePrivateMember(int value) {
        somePrivateMember = value;
    }
};

class B {
public:
    void someMemberFunction() {
        A a;
        // 可以通过访问器函数间接访问A类中的私有成员
        a.setSomePrivateMember(10);
        int value = a.getSomePrivateMember();
    }
};