c++ - vector c++ 的奇怪行为

Question

我有一个问题要问你。假设我有一个 AwesomeData vector ，AwesomeData 类包含一个 AwesomeData vector 。如果我尝试访问第一个 vector 中的 vector ，它无法正常工作。据我所知，这里并不清楚一个更明确的例子:

struct AwesomeData
{
public:
    AwesomeData()
    : beautifulInt(3)
    {}

    int beautifulInt;
    vector<AwesomeData> someVector;
};

int main()
{
    vector<AwesomeData> tata;
    AwesomeData toto;

    toto.someVector.push_back(AwesomeData());
    toto.someVector.push_back(AwesomeData());
    toto.someVector.push_back(AwesomeData());

    tata.push_back(AwesomeData());
    tata.push_back(toto);
    tata.push_back(AwesomeData());


    // So, now tata should containt the data of someVector of toto (3 default    
    // AwesomeData). Instead of that, his capacity is equal to 3, but his
    // size = 0. So, what's wrong ?
    tata = tata[1].someVector;
}

但是，嘿，这还不是全部!我找到了变通方法，但我不知道它为什么起作用。

struct AwesomeData
{
public:
    AwesomeData()
        : beautifulInt(3)
    {}

    int beautifulInt;
    vector<AwesomeData> someVector;
};

int main()
{
    vector<AwesomeData> tata;
    AwesomeData toto;

    toto.someVector.push_back(AwesomeData());
    toto.someVector.push_back(AwesomeData());
    toto.someVector.push_back(AwesomeData());

    tata.push_back(AwesomeData());
    tata.push_back(toto);
    tata.push_back(AwesomeData());


    // If we use a second vector to temporaly stock the vector of toto,
    // everything work as expected
    vector<AwesomeData> tempVector;

    tempVector = tata[1].someVector;
    tata = tempVector;
}

所以有人有想法吗？

非常感谢

Answer 1

标准容器不允许您使用不完整的类型实例化它们。在你的例子中 AwesomeData当您尝试实例化 std::vector<AwesomeData> 时未完全定义.

要实现这一点，您可以查看 boost::container图书馆。

参见 Boost::container