Class 来自字符串

Question

我遇到了一个问题，我不确定从这里该何去何从。

In this program, you are going to create a class called mystring, which is derived from class string. Class mystring should include:

A private data member id, which is an integer, representing the ID of a string (see example in function main()).

A public method, constructor mystring(int, char *), which has two parameters: an integer (int) and a string (char *). It should (1) call base class constructor using the string parameter (char *) and (2) assign integer parameter (int) to id.

A public method int getid(), which returns id of class mystring.

这是我目前所拥有的

class mystring : public string
{
  private:
    int id;
  public:
    mystring(int id, char *words);
    int getid();
};

mystring::mystring(int id, char *words)
{
  string a (words);
  this->id = id;
}

int mystring::getid()
{
  return id;
}

// If your class is implemented correctly, the main program should work as
//the followings
int main()
{
  mystring x(101, "Hello Kitty");   // “hello Kitty” has an ID 101
  cout << x.getid() << endl;            //display 101
  cout << x << endl;                    //display string value: “Hello Kitty”
  cout << x.length() << endl;       //display length of the string: 11
  return 0;
}

我明白了

101

0

Answer 1

在您的构造函数中，您没有为您的实例调用 std::string 基本构造函数，您只是创建一个本地字符串，然后将其丢弃。

改变这个：

mystring::mystring(int id, char *words)
{
    string a (words); //creates a local string called a
    this->id = id;    //initializes id
}

要使用初始化列表，像这样：

mystring::mystring(int id, char *words) :
    string(words), //calls the string base constructor
    id(id)         //initializes id
{}

Class 来自字符串

Class derived from string

c++

string

class

derived