如何从txt文件中提取带有逗号分隔符的字符串并将用逗号分隔符分隔的每个元素解析为类构造函数

Question

来源：文本文件存储帐户信息列表。例如：

10041249,Mr,Vincent,Rogan,Rogan Locksmiths Ltd,Nell,5287.000000,,491.691000,
10021250,Mrs,Adele,Cunningham,Cunningham Demolition Ltd,Dr Scott,2941.000000,,273.513000,
10051251,Mr,Rodney,Shaw,Shaw Meat Packaging Ltd,Eddie,7552.000000,,740.096000,
10001252,Mrs,Christine,Nichols,Nichols Scaffolding Ltd,Brad,6723.000000,Eddie:Brad:,672.300000,
10021253,Mr,Alexander,Marshall,Marshall Chemicals Ltd,Dr Scott,1768.000000,,173.264000,
10021254,Ms,Shirley,Hagman,On Point Sportswear Ltd,Dr Scott,52.000000,,5.200000,
....
....
....

如何从txt文件中提取带有逗号分隔符的字符串并将由逗号分隔符分隔的每个元素解析为类构造函数？

我尝试使用 stringstream 从每一行中提取数据。但这不起作用。 我得到的 EmployeeAccount 类如下：

#include <iostream>
#include <sstream>
#include <string>

using namespace std;

class EmployeeAccount {
private:
    //member variable
    string acountNumber;
    string title; 
    string firstname; 
    string lastname; 
    string company; 
    string salesperson; 
    double purchaseValue; 
    string prev_salestaff; 
    double commission; 

public:

    //overload constructor
    EmployeeAccount(const string& employeeAccountInfo)
    {
        string str;
        stringstream employeeAccountStream(employeeAccountInfo);
        while (getline(employeeAccountStream, str, ','))
        {
            stringstream sso(str); 
                sso >> acountNumber; 
                sso >> title; 
                sso >> firstname; 
                sso >> lastname; 
                sso >> company; 
                sso >> salesperson; 
                sso >> purchaseValue; 
                sso >> prev_salestaff; 
                sso >> commission; 
        }
    }
    //Access methods
    string getAccountNumber() { return acountNumber; }; 
    string getTitle() { return title; }; 
    string getFirstname() { return firstname; }; 
    string getLastname() { return lastname; }; 
    string getCompany() { return company; }; 
    double getPurchaseValue() { return purchaseValue; }; 
    string getPrev_salesstaff() { return prev_salestaff; }; 
    double getCommission() { return commission; }; 
    string getAccountDetail() { return acountNumber + " " + title + " " + firstname + " " + lastname + " " + company;};

    //Destructor
    ~EmployeeAccount() {};
};

测试代码是这样的：

    cout << testEmployee.getAccountDetail() << endl;
    cout << testEmployee.getAccountNumber() << endl;
    cout << testEmployee.getTitle() << endl;
    cout << testEmployee.getFirstname() << endl;
    cout << testEmployee.getLastname() << endl;
    cout << testEmployee.getCompany() << endl;
    cout << testEmployee.getPurchaseValue() << endl;
    cout << testEmployee.getPrev_salesstaff() << endl;
    cout << testEmployee.getCommission() << endl;
}

Answer 1

解析 CSV 文件是一个老话题了。您将在 stackoverflow 上找到至少 100 个带有代码示例的答案。通常，您会通过函数 std::getline 找到解决方案。请阅读此处的文档。它可以从 std::ifstream 读取字符，直到达到分隔符（在我们的例子中为逗号 ,），然后将结果（不带逗号）存储在字符串并丢弃流中的逗号。所以，把它扔掉。这些字符将存储在 std::string 中。如果需要数字或其他类型，我们需要使用适当的函数将字符串转换为其他类型。

示例：我们有一个由字符“1”、“2”和“3”组成的字符串，即“123”。引号表示字符串类型。如果我们想将此字符串转换为整数，我们可以使用例如函数 std::stoi。

就您而言，您有 2 个双精度值。因此，我们将文件的输入拆分为字符串，然后使用函数 std::stod 转换其中包含双精度值的 2 个字符串。

您还需要了解的是，通常使用两步方法。这样做是为了防止从一个 csv 行中提取所有字符串部分而引起的潜在问题。因此，

• 我们首先读取完整的行，
• 然后将该行放入 std::istringstream 中，最后
• 读取输入并从那里拆分 CSV。

然后，剩下的就简单了。只需使用 std::getline 即可获取您需要的数据。

最后但并非最不重要的一点是，要读取该文件，我们只需打开它，逐行读取，创建一个“EmployeeAccount”并将其推送到 std::vector

最后，我们进行一些调试输出。

请参阅下面可能的潜在实施建议之一：

#include <iostream>
#include <sstream>
#include <fstream>
#include <string>
#include <vector>


class EmployeeAccount {
private:
    //member variable
    std::string acountNumber;
    std::string title;
    std::string firstname;
    std::string lastname;
    std::string company;
    std::string salesperson;
    double purchaseValue; 
    std::string prev_salestaff;
    double commission; 

public:

    //overload constructor
    EmployeeAccount(const std::string& employeeAccountInfo)
    {
        std::istringstream employeeAccountStream(employeeAccountInfo);
        std::getline(employeeAccountStream, acountNumber, ',');
        std::getline(employeeAccountStream, title, ',');
        std::getline(employeeAccountStream, firstname, ',');
        std::getline(employeeAccountStream, lastname, ',');
        std::getline(employeeAccountStream, company, ',');
        std::getline(employeeAccountStream, salesperson, ',');
        std::string temp;
        std::getline(employeeAccountStream, temp, ',');
        purchaseValue = std::stod(temp);
        std::getline(employeeAccountStream, prev_salestaff, ',');
        std::getline(employeeAccountStream, temp, ',');
        commission = std::stod(temp);
    }
    //Access methods
    std::string getAccountNumber() const { return acountNumber; };
    std::string getTitle()  const { return title; };
    std::string getFirstname()  const { return firstname; };
    std::string getLastname()  const { return lastname; };
    std::string getCompany()  const { return company; };
    double getPurchaseValue()  const { return purchaseValue; };
    std::string getPrev_salesstaff()  const { return prev_salestaff; };
    double getCommission()  const { return commission; };
    std::string getAccountDetail()  const { return acountNumber + " " + title + " " + firstname + " " + lastname + " " + company;};

    //Destructor
    ~EmployeeAccount() {};
};
int main() {
    std::ifstream ifs{ "accounts.txt" };
    if (ifs) {

        // Here we will store all accounts
        std::vector<EmployeeAccount> accounts{};

        // Read the file line by line
        std::string line{};
        while (std::getline(ifs, line)) {

            // Create one account by splitting the input line
            EmployeeAccount account(line);

            // Add the new accounts to the vector of accounts
            accounts.push_back(account);
        }

        // Debug output. For all accounts that we read, output all data
        for (const EmployeeAccount& account : accounts) {

            std::cout << "\n--------------------------\n"
             << account.getAccountDetail() << '\n'
             << account.getAccountNumber() << '\n'
             << account.getTitle() << '\n'
             << account.getFirstname() << '\n'
             << account.getLastname() << '\n'
             << account.getCompany() << '\n'
             << account.getPurchaseValue() << '\n'
             << account.getPrev_salesstaff() << '\n'
             << account.getCommission() << '\n';
        }
    }
    else
        std::cerr << "\n*** Error: Could not open source file\n\n";
}