Creating Observables from the scratch

So far, we have written code that create an Observable Stream from a range object or STL containers. Let's see how we can create an Observable Stream from the scratch. Well, almost:

// ObserverFromScratch.cpp 
#include "rxcpp/rx.hpp" 
#include "rxcpp/rx-test.hpp" 
int main() { 
      auto ints = rxcpp::observable<>::create<int>( 
                  [](rxcpp::subscriber<int> s){ 
                       s.on_next(1); 
                       s.on_next(4); 
                       s.on_next(9); 
                       s.on_completed(); 
                 }); 
    ints.subscribe( [](int v){printf("OnNext: %dn", v);}, 
                             [](){printf("OnCompletedn");}); 
} 

The preceding program calls the on_ext method to emit a series of numbers that are perfect squares. Those numbers (1,4,9) will be printed to the console.

Concatenating Observable Streams

We can concatenate two Streams to form a new Stream and this can be handy in some...