[英]Bad cast while getting data from PostgreSQL database using SOCI
我在PostgreSQL中有一个数据库。 而且我有sql查询(btw在PostgreSQL中很好用, 因此sql代码没有错 ):
SELECT COUNT(*) as size, creation_date FROM item INNER JOIN raf_item USING (id) INNER JOIN item_detail USING (id) GROUP BY creation_date;
其中创建日期定义为creation_date Date;
在PostgreSQL中。例如,查询返回(取决于我在数据库中拥有的内容):
size | creation_date
21 | 12-31-2012
18 | 04-03-2002
我正在使用SOCI + C ++从此查询中获取数据。 我的整个C ++代码:
#include <iostream>
#include <cstdlib>
#include <soci.h>
#include <string>
#include <postgresql/soci-postgresql.h>
using namespace std;
bool connectToDatabase(soci::session &sql, string databaseName, string user, string password)
{
try
{
sql.open(soci::postgresql, "dbname=" +databaseName + " user="+user + " password="+password);
}
catch (soci::postgresql_soci_error const & e)
{
cerr << "PostgreSQL error: " << e.sqlstate() << " " << e.what() << std::endl;
return false;
}
catch (std::exception const & e)
{
cerr << "Some other error: " << e.what() << std::endl;
return false;
}
return true;
}
void getDataFromDatabase(soci::session &sql)
{
soci::row r;
sql << "select count(*) as size, creation_date from item inner join raf_item using (id) inner join item_detail using (id) group by creation_date;", soci::into(r);
for(std::size_t i = 0; i != r.size(); ++i)
{
cout << r.get<int>(i);
tm when = r.get<tm>(i);
cout << asctime(&when);
}
}
int main(int argc, char **argv)
{
soci::session sql;
bool success = connectToDatabase(sql, "testdb", "testuser", "pass");
if (success)
{
cout << "Connected.\n";
getDataFromDatabase(sql);
}
else
cout << "Not connected.\n";
return 0;
}
但是,当我尝试运行该应用程序时,出现了此错误(编译很好):
抛出'std :: bad_cast'实例后终止调用
what():std :: bad_cast中断(核心已转储)
请帮助,当编译正常时,我真的不知道该如何解决。
也许问题在于creation_date是DATE,而tm也保留了时间...? 如果是这样,该如何解决?
好的,我自己解决了!:)
继承人实际上可以正常工作的代码(我只用下面的代码补充了getDataFromDatabase
):
void getDataFromDatabase(soci::session &sql)
{
long size;
string date;
soci::row r;
sql << "select count(*) as size, creation from item inner join raf_item using (id) inner join item_detail using (id) group by creation;", soci::into(r);
for(std::size_t i = 0; i != r.size(); ++i)
{
const soci::column_properties & props = r.get_properties(i);
cout << '<' << props.get_name() << '>';
switch(props.get_data_type())
{
case soci::dt_string:
cout << r.get<std::string>(i);
break;
case soci::dt_double:
cout << r.get<double>(i);
break;
case soci::dt_integer:
cout << r.get<int>(i);
break;
case soci::dt_unsigned_long:
cout << r.get<unsigned long>(i);
break;
case soci::dt_long_long:
cout << r.get<long long>(i);
size = r.get<long long>(i);
break;
case soci::dt_date:
std::tm when = r.get<std::tm>(i);
cout << asctime(&when);
date = asctime(&when);
break;
}
cout << "\n" << size << "\n";
cout << "\n" << date << "\n";
}
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