c++ - 我将如何在 C++ 中实现动态绑定(bind)的这种使用？

Question

我已经尝试了很多事情并思考了一段时间，但我就是想不出正确的语法/逻辑。

我有一个基类和两个派生类。我正在使用动态绑定(bind)制作一个存储所有 3 个类实例的 vector 。然后，我从文件中读取，它指定它属于哪个类(我将使用 if 语句检查文件中的字符串，例如“base”、“der1”、“der2”)。然后它将其压入堆栈。

如果每个类只有一个，我可以管理以上内容，但是，每个类都有多个。因此，类似下面的代码将不起作用:

vector<Base*> myVec;

然后:

Base *b = new Base;
Der1 *d1 = new Der1;
Der2 *d2 = new Der2;

//read the file and fill in the classes data members

myVec.push_back(b);
myVec.push_back(d1);
myVec.push_back(d2);

上面的代码只会阅读每种类型的类(class)一次，然后继续进行。我将如何实现以下内容:

for(int i = 0; i < lines; i++) //lines = how many lines in file
{
    cin.get(whatType, ':'); //reads a string up to the delim char :

    if(whatType == "Base")
    {
        //read line and fill rest of data members...
        myVec.push_back(b);
    }
    else if(whatType == "Der1")
    {
        //read line and fill rest of data members...
        myVec.push_back(d1);
    }
    if(whatType == "Der2")
    {
        //read line and fill rest of data members...
        myVec.push_back(d2);
    }
}

但是，当再次读入相同的类类型时，前一个会被覆盖，而且它是指向一个实例的指针？所以最后输出是不正确的。我希望它们都是唯一的实例。

我该怎么做？我不知道。

Answer 1

您应该每次都创建类的新实例，如下所示:

    vector<Base*> myVec;

    // main loop
    for (int i = 0; i < lines; i++) //lines = how many lines in file
    {
      cin.get(whatType, ':'); //reads a string up to the delim char :

      if(whatType == "Base")
      {
        Base *b = new Base;
        //read line and fill rest of data members...
        myVec.push_back(b);
      }
      else if(whatType == "Der1")
      {
        Der1 *d1 = new Der1;
        //read line and fill rest of data members...
        myVec.push_back(d1);
      }
      if(whatType == "Der2")
      {
        Der2 *d2 = new Der2;
        //read line and fill rest of data members...
        myVec.push_back(d2);
      }
    }

    // deleting pointers
    for (int i = 0; i < myVec.size(); ++i)
    {
      delete myVec[i];
    }