向量的stange行为C++

Question

我有一个问题给你。假设我有一个AwesomeData矢量，AwesomeData类包含一个AwesomeData矢量。如果我尝试访问第一个向量内的向量，它不能正常工作。据我所知这里有一个更明确的例子：

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，这不是全部！我发现了一个工作，但我不知道它为什么工作。

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; 
} 

那么，任何人有一个想法？

非常感谢

Answer 1

标准容器不允许您使用不完整类型实例化它们。在你的例子中，当你尝试实例化一个std::vector<AwesomeData>时，AwesomeData没有完全定义。

要达到此目的，您可以查看boost::container库。

看到Boost::container