c++ - 搜索时 vector 键丢失

Question

我的类中有一个 vector 数组，用于保存指向特定对象指针的指针。

该类应包含允许添加、删除和查找内部对象的方法。现在的类如下所示:

class VectorKontener: public Kontener <VectorKontener> {
protected:
    int find(Obiekt &n) {
        cout << endl << "---------------------" << endl << "Running find method loop!" << endl;

        for (int i = 0; i < stos.size(); i++) {
            cout << "Now running for id: " << stos[i]->getId() << endl;
            if (stos[i] == &n) return i;
        }
        return -1;
    }
public:
    VectorKontener::VectorKontener(Obiekt &n) {
        add(n);
    }

    VectorKontener add(Obiekt &n) {
        cout << "Adding: " << n.getId() << endl;

        stos.push_back(&n);

        return *this;
    }

    int checkPresent(Obiekt &n) {
        return this->find(n) != -1;
    }

    VectorKontener remove(Obiekt &n) {
        if (this->checkPresent(n)) {
            stos.erase(stos.begin() + this->find(n));
        }
        else
            cout << endl <<"ELEMENT NOT IN CONTAINER" << endl;

        return *this;
    }

    VectorKontener display() {
        cout << endl << "===DISPLAY===" << endl;
        for (int i = 0; i < stos.size(); i++) {
            stos[i]->display();
        }

        return *this;
    }
};

但是当运行测试数据时:

void Zad3()
{
    Obiekt 
        obj1(5), 
        obj2(23), 
        obj3(234), 
        obj4(33);


    cout << endl << "1. Class init" << endl;
    VectorKontener k1(obj1);

    cout << endl << "2. Adding other objects into array" << endl;

    k1
        .add(obj2)
        .add(obj3)
        .display();

    cout << endl << "3. Element remove attempt" << endl;
    k1
        .remove(obj2)
        .display();

    getchar();
}

输出看起来像这样:

1. Class init
Adding: 5

2. Adding other objects into array
Adding: 23
Adding: 234

===DISPLAY===
This object has id: 5
This object has id: 23
This object has id: 234

3. Element remove attempt

---------------------
Running find method loop!
Now running for id: 5
Now running for id: 23

---------------------
Running find method loop!
Now running for id: 5
Now running for id: 23

===DISPLAY===
This object has id: 5

尽管 stos.size() 显示正确的值 (2)。

我不是 cpp 专家，公平地说远非如此，我知道这可能是一个相当笨拙的问题，但我真的没有办法让它正常工作。

任何帮助都会非常棒

Answer 1

问题在于函数返回对象的拷贝，这意味着在链式add 调用中原始对象未被修改(在第二个和任何后续函数中调用)，而是在每个函数调用时创建一个临时的，然后立即销毁。

简单的解决方法是将返回值更改为引用，例如:对于添加函数:

VectorKontener& add(Obiekt &n) {

代替

VectorKontener add(Obiekt &n) {

其他功能也有类似的变化。