group_by.cpp

#include <rpp/rpp.hpp>
 
#include <iostream>

int main()
{
    rpp::source::just(1, 2, 3, 4, 5, 6, 7, 8)
        | rpp::operators::group_by([](int v) { return v % 2 == 0; })
        | rpp::operators::subscribe([](auto grouped_observable) {
              auto key = grouped_observable.get_key();
              std::cout << "new grouped observable " << key << std::endl;
              grouped_observable.subscribe([key](int val) {
                  std::cout << "key [" << key << "] Val: " << val << std::endl;
              });
          });
    // Output: new grouped observable 0
    //         key [0] Val: 1
    //         new grouped observable 1
    //         key [1] Val: 2
    //         key [0] Val: 3
    //         key [1] Val: 4
    //         key [0] Val: 5
    //         key [1] Val: 6
    //         key [0] Val: 7
    //         key [1] Val: 8
    //
    struct person
    {
        std::string name;
        int         age;
    };
    rpp::source::just(person{"Kate", 18},
                      person{"Alex", 25},
                      person{"Nick", 18},
                      person{"Jack", 25},
                      person{"Tom", 30},
                      person{"Vanda", 18})
        | rpp::operators::group_by([](const person& v) { return v.age; }, [](const person& v) { return v.name; })
        | rpp::operators::subscribe([](auto grouped_observable) {
              grouped_observable.subscribe([age = grouped_observable.get_key()](const std::string& name) {
                  std::cout << "Age [" << age << "] Name: " << name << std::endl;
              });
          });
 
    // Output: Age [18] Name: Kate
    //         Age [25] Name: Alex
    //         Age [18] Name: Nick
    //         Age [25] Name: Jack
    //         Age [30] Name: Tom
    //         Age [18] Name: Vanda
    return 0;
}