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我正在使用 SQLite3 后端在 C++ SOCI 库中尝试对象关系映射。但是，当我尝试从数据库REAL值加载为 C++ 的 double 时，std::bad_cast就会抛出异常。

完整代码：

#include <iostream>
#include <string>
#include <exception>
#include <soci/soci.h>
#include <soci/sqlite3/soci-sqlite3.h>

using namespace std;
using namespace soci;


struct Employee
{
    int id;
    std::string name;
    double salary;
};

ostream& operator<<(ostream& o, const Employee& employee)
{
    return o << "Employee(" << employee.id << "):" << employee.name << ", earns: " << employee.salary;
}

namespace soci
{
    template<>
    struct type_conversion<Employee>
    {
        typedef values base_type;

        static void from_base(const values & v, indicator /* ind */, Employee & employee)
        {
            employee.id = v.get<int>("ID");
            employee.name = v.get<std::string>("Name");
            cout << "Type: " << v.get_properties("Salary").get_data_type() << endl; // the output is 0, so the type is soci::dt_string but not soci::dt_double
            if (v.get_indicator("Salary") == i_ok)
                employee.salary = v.get<double>("Salary");
        }

        static void to_base(const Employee& employee, values& v, indicator& ind)
        {
            v.set("ID", employee.id);
            v.set("Name", employee.name);
            v.set("Salary", employee.salary, employee.salary == 0. ? i_null : i_ok);
            ind = i_ok;
        }
    };
}

int main()
{
    try
    {
        soci::session sql(sqlite3, "employees.db");
        sql << "CREATE TABLE IF NOT EXISTS Employees("  \
               "ID INT PRIMARY KEY     NOT NULL," \
               "Name           TEXT    NOT NULL," \
               "Salary         REAL);";
        sql << "INSERT INTO Employees (ID, Name, Salary) "  \
               "VALUES (1, 'Janusz Korwin-Mikke', 12000.01 ); ";

        Employee employee = {};
        sql << "SELECT * FROM Employees WHERE ID = 1;", into(employee);
        cout << employee << endl;
    }
    catch (const exception &e)
    {
        cerr << "Error: " << e.what() << endl;
    }
}

当我运行代码时，我看到std::bad_cast行中抛出的异常：

employee.salary = v.get<double>("Salary");

尽管在数据库中它是REAL类型。当我将行更改为：

employee.salary = atof(v.get<std::string>("Salary").c_str());

我正在使用 SOCI-4.0.0，但以前的版本 3.2.3 也有同样的问题，我在 Windows 7 和 MinGW 编译器 7.3.0 上使用 SQLite3

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