按姓氏对列表进行排序

很多小错误。

公共部分。

在C 公共中，其次是'：'标记部分。另外，您需要包括string定义。居住在std::名称空间中。

  public: std::string firstName;
  public: std::string lastName;
  public: std::string title;
  public: std::string phonenumber;

C 是类型的非常学费。

您需要指定所有参数的类型：

EmployeeInformation(string const& firstName, string const & lastName, string const& title, string const& phonenumber)

未知名称：

this->initials = title;
  //  ^^^^^^^^   Not a member of this class. Did you mean title.
this->id = phoneumber;
  //  ^^         Not a member of this class. Did you mean phoneumber

语句由';''

return a.lastName < b.lastName
                       //      ^^^^^   missing here.

将其修复的内容编译后。但是我将固定版本进行代码评论以进行更详细的分解。

当所有完整的主看起来像这样时：

int main(int argc, char**argv)
{
    std::ifstream file("employees.txt");
    // Read data into vector
    std::vector<EmployeeInformation> employees(std::istream_iterator<EmployeeInformation>(file),
                                               (std::istream_iterator<EmployeeInformation>()));
    // Sort container.
    std::sort(std::begin(employees), std::end(employees),
              [](EmployeeInformation const& lhs, EmployeeInformation const& rhs) { return lhs.lastName < rhs.lastName;});
    // Copy container to stream.
    std::copy(std::begin(employees), std::end(employees),
              std::ostream_iterator<EmployeeInformation>(std::cout));
}

您的课程未正确声明。例如，您无法从构造函数参数中省略数据类型。

您也没有正确读取文件。

尝试更多类似的东西：

#include <vector>
#include <algorithm>
#include <iostream>
#include <fstream>
#include <string>
#include <sstream>
using namespace std;
class EmployeeInformation
{
public:
    string firstName;
    string lastName;
    string title;
    string phoneNumber;
    EmployeeInformation(const string &_firstName, const string &_lastName, const string &_title, const string &_phonenumber) :
        firstName(_firstName),
        lastName(_lastName),
        title(_title),
        phoneNumber(_phoneNumber)
    {
    }
};
int main(int argc, char**argv)
{
    ifstream file;
    file.open("employees.txt");
    if (!file.is_open())
    {
        cout << "Error opening file";
        return 0;
    }
    vector<EmployeeInformation> employees;
    string line;
    while (getline(file, line))
    {
        string firstName, lastName, title, phonenumber;
        istringstream iss(line);
        iss >> firstName >> lastName >> title >> phonenumber;
        EmployeeInformation person(firstName, lastName, title, phonenumber);
        employees.push_back(person);
    }
    sort(employees.begin(), employees.end(), [](const EmployeeInformation &a, const EmployeeInformation &b) { return a.lastName < b.lastName; });
    for (EmployeeInformation i : employees)
    {
        // print person info in sorted order
        cout << i.lastName << " " << i.firstName << " " << i.title << " " i.phoneNumber << endl;
    }
    return 0;
}

访问修饰符的语法不正确（您使用的是Java样式而不是C ）。在C 中，您会声明这样的完全公开课程：

 class EmployeeInformation {
 public:
   string firstName;
   string lastName;
   string title;
   string phonenumber;
   //...
};

如果您确实想公开所有数据，则也可以使用结构而不是类，因为默认情况下结构的成员是公开的。

首先，您在类中的所有变量声明都是错误的。

 class EmployeeInformation {
public:
string firstName;
string lastName;
string title;
string phonenumber;
EmployeeInformation(string &firstName,string &lastName,string &title,string &phonenumber)
{
this->firstName = firstName;
this->lastName = lastName;
this->title = title;            //there is no variable named initial in class
this->phonenumber = phonenumber; //there is no variable named id in class
}
};

然后您缺少半分离。

sort(employees.begin(), employees.end(), [](EmployeeInformation a, EmployeeInformation b) { return a.lastName < b.lastName; });  //there should be a semicolon after return statement