錯誤：請求用於連接的構件「查詢」，這是無級類型「MYSQL *」

Question

// todo: create the connection here 

// Construct the query string. You were already doing this in your code 
std::ostringstream query_builder; 
query_builder << "select pipe_id from pipe where version_id='" << id << "'"; 

// Convert the ostringstream to a string 
std::string query_string = query_builder.str(); 

// Construct a query object with the query string 
mysqlpp::Query query = connection.query(query_string); 

// Perform the query 
mysqlpp::StoreQueryResult result = query.store(); 
for(size_t i = 0; i < result.num_rows(); i++) 
    std::cout << result[i]["version_id"] << result[i]["pipe_id"] << std::endl; 

我正在錯誤

error: request for the member 'query' in connection which is non-class type ' 
MYSQL*' 

at line 
**mysqlpp::Query query = connection.query(query_string);** 

Answer 1

connection是一個指針;您需要使用->操作：

connection->query(query_string)