c++ - 重载 = 运算符(operator)，无法让它工作

Question

我试图在下面的代码中重载第 9 行的 =operator:

void searchContact(vector<Person> &people){
    string searchTerm;
    vector<Person>::iterator it;

    cout << endl;
    cout << "Enter search term: ";
    getline(cin, searchTerm);

    it = find(people.begin(), people.end(), searchTerm);

    if (it != people.end()){
        cout << "Element found in: " << *it << '\n';
    }else{
        cout << "Element not found\n";
    }
}

我的做法是这样的:

  int data;

  Person& operator=(Person& a) { return a; }
  Person& operator=(int a) {
    data = a;
    return *this;
  }

我收到这个错误:

class.cpp:129:30: error: ‘Person& operator=(Person&)’ must be a nonstatic member function
   Person& operator=(Person& a) { return a; }
                              ^
class.cpp:130:26: error: ‘Person& operator=(int)’ must be a nonstatic member function
   Person& operator=(int a) {

我的方法有什么问题，还是我从一开始就做错了？

Answer 1

首先，您重载了错误的运算符。 std::find()使用 operator== (比较)而不是 operator= (任务)。而且，鉴于您正在传递 std::string至 std::find() , 你需要一个 operator==这需要 std::string作为输入，不是 Person .

其次，您正在尝试将运算符实现为一元运算符，这意味着它们必须是您的 Person 的非静态成员。类(class)。编译器提示他们不是。

三、如果std::find()找到匹配项，您正在传递 *it至 std::cout , 所以你需要一个重载的 operator<<这需要 Person用于输出。

尝试这样的事情:

class Person
{
public:
    ...

    bool operator==(const string &rhs) const
    {
        // compare members of *this to rhs as needed...
        return ...; // true or false
    }

    /* alternatively:
    friend bool operator==(const Person &lhs, const string &rhs)
    {
        // compare members of lhs to rhs as needed...
        return ...; // true or false
    }
    */

    friend ostream& operator<<(ostream &out, const Person &p)
    {
        // output p to out as needed...
        return out;
    }

    ...
};

然后您的搜索代码将起作用:

void searchContact(vector<Person> &people)
{
    cout << endl;
    cout << "Enter search term: ";

    string searchTerm;
    getline(cin, searchTerm);

    vector<Person>::iterator it = find(people.begin(), people.end(), searchTerm);    

    if (it != people.end()) {
        cout << "Element found in: " << *it << '\n';
    } else {
        cout << "Element not found\n";
    }
}