Reflection - MichaelMiller-/sec21 GitHub Wiki
The idea behind this library is not to change existing data structures, but to achieve reflection functionality via a simple template specialization.
Note: Based on this development, another library has been created that makes use of the Reflection TS. Feel free to check it out. Link
// example class / existing code
struct user
{
std::string name{};
std::string password{};
int karma{};
double cash{};
};
struct rectangle
{
double width{};
double height{};
};The existing classes can be made known to the system via template specialization.
// specialize 'sec21::reflection::table' template for those classes
//
template <>
struct sec21::reflection::table<user>
{
static constexpr auto name = "user";
struct columns
{
using name = column<"name", &user::name, primary_key, not_null>;
using password = column<"password", &user::password, not_null>;
using karma = column<"karma", &user::karma>;
using cash = column<"cash", &user::cash>;
};
using metainfo = std::tuple<
columns::name,
columns::password,
columns::karma,
columns::cash>;
};
//
template <>
struct sec21::reflection::table<rectangle>
{
static constexpr auto name = "rectangle";
struct columns
{
using width = column<"width", &rectangle::width>;
using height = column<"height", &rectangle::height>;
};
using metainfo = std::tuple<columns::width, columns::height>;
};Once the classes have been made known to the reflection system, it is very easy to develop generic algorithms that take advantage of the system.
// generic algorithm that works with any type that provides a reflection specialization
template <typename T>
void print_first_column(std::vector<T> const& values)
{
using namespace sec21;
using reflection_t = typename reflection::table<T>::metainfo;
for (auto const& value : values)
{
std::cout << reflection::get_column<0>(value) << std::endl;
}
}
int main()
{
{
std::vector<user> input{
{ "John Doe", "secret", 42, 0 },
{ "Max Mustermann", "****", 1, 45'678 }
};
print_first_column(input);
}
{
std::vector<rectangle> input{
{ 3.14, 4.15 },
{ 1.41, 2.77 }
};
print_first_column(input);
}
return 0;The output is:
John Doe
Max Mustermann
3.14
1.41