C++ 11 可变参数模板和 boost::any 实现可变参数函数

 1 class SqlHelper
 2 {
 3 public:
 4     template <typename... Params>
 5     static bool preparedExecute(sql::PreparedStatement* pstmt, Params... parameters)
 6     {
 7         return doPreparedExecute(pstmt, 1, parameters...);
 8     }
 9
10 private:
11     template <typename... Params>
12     static bool doPreparedExecute(sql::PreparedStatement* pstmt, int i, boost::any value, Params... parameters)
13     {
14         setAnyType(pstmt, i, value);
15         return doPreparedExecute(pstmt, ++i, parameters...);
16     }
17
18     static bool doPreparedExecute(sql::PreparedStatement* pstmt, int i, boost::any value)
19     {
20         assert(pstmt != nullptr);
21         setAnyType(pstmt, i, value);
22         return pstmt->execute();
23     }
24
25     static void setAnyType(sql::PreparedStatement* pstmt, int i, boost::any value)
26     {
27         assert(pstmt != nullptr);
28
29         if (value.type() == typeid(int32_t))
30         {
31             pstmt->setInt(i, boost::any_cast<int32_t>(value));
32         }
33         else if (value.type() == typeid(std::string))
34         {
35             pstmt->setString(i, boost::any_cast<std::string>(value));
36         }
37         else if (value.type() == typeid(char const *))
38         {
39             pstmt->setString(i, boost::any_cast<char const *>(value));
40         }
41
42         // ......
43     }
44 };

其实就是在模板实例化的时候递归实例化

调用方法

1 SqlHelper::preparedExecute(pstmt.get(), "1", 1u, 1f, 1.0, std::string("1"));
2 SqlHelper::preparedExecute(pstmt.get(), 1.0, "1", 1f, 1u, std::string("1"), std::string("2"));

C++ 11 可变参数模板和 boost::any 实现可变参数函数