Question

我试图解决我在c ++中关于类的问题。为了防止复杂的问题，我会为我的问题编写一个示例代码。现在这是我的问题。

class sample1
{
 public:
 //getter,setter,constructor and destructor functions
 private:
 string label; 

}

class sample2 // in sample2.h #include "sample1" is exist.
{
 public:
  //getter setter constructors and destructors.
  void addSample1(string label);
 private:
  vector<sample1*> sample1's;
}

现在，正如您所看到的，我想用sample1指针填充sample2类中的向量。我尝试使用以下代码执行此操作但是，显然vector只能存储一个指针，因为在exSample1函数的exacu之后，指针丢失了。这是我的代码不起作用。

void addSample1(string label)
{       
        sample1  samp1(label);
    sample1 * n_pointer=new samp1(label);
    n_pointer=&samp1;
    sample1's.push_back(n_pointer);
}

有没有人可以帮我解决问题？提前谢谢

Answer 1

您的addSample应该只是：

void addSample1(string label)
{       
    sample1s.push_back(new sample1(label));
}

一旦你完成它们或者在向量中存储智能指针，你必须小心并删除那些指针。

你在addSample做的事情非常糟糕。

void addSample1(string label)
{       
    // creates a local sample1 object on the stack
    sample1  samp1(label);
    //creates a sample1 object on heap
    sample1 * n_pointer = new sample1(label);
    // overwrites the sample1 pointer with the address of the local object
    // this will leak memory as you have lost the pointer to the dynamically allocated object.
    n_pointer=&samp1;
    //pushes the pointer that points to the local object into the vector
    sample1s.push_back(n_pointer);

   // here the local object is destroyed so now the pointer in the vector 
   // points to deallocated space, accessing it will result in undefined behaviour
}

Answer 2

怎么样

void addSample1(string label)
{       
    sample1's.push_back(new sample1(label));
}

Answer 3

这应该有效：

void sample2::addSample1(string label)
{       
    sample1* n_pointer=new sample1(label);
    sample1s.push_back(n_pointer);
}

重命名您的成员变量：

private:
  vector<sample1*> sample1s;

c ++将一个类定义到另一个类

3 个答案: