Observable: Generic observable objects for C++

If you want to write code in a reactive style or just implement the observer pattern, this is for you.

Quick start

The library is header-only and has no dependencies; copy the include/observable directory into your include path and you're set.

Example:

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

using namespace std;
using namespace observable;

int main()
{
    auto sub = subject<void(string)> { };
    sub.subscribe([](auto const & msg) { cout << msg << endl; });

    // "Hello world!" will be printed on stdout.
    sub.notify("Hello world!");

    auto a = value<int> { 5 };
    auto b = value<int> { 5 };
    auto avg = observe(
                    (a + b) / 2.0f
               );
    auto eq_msg = observe(
                    select(a == b, "equal", "not equal")
                   );

    avg.subscribe([](auto val) { cout << val << endl; });
    eq_msg.subscribe([](auto const & msg) { cout << msg << endl; });

    // "10" and "not equal" will be printed on stdout in an
    // unspecified order.
    b = 15;

    return 0;
}

Documentation

You can access the documentation here: https://danieldinu.com/observable/.

What's with the CMake files?

The library is using CMake to build the tests, benchmarks and documentation. You won't need CMake if you don't want to work on the library as a developer.

Why not just use Boost.Signals2 or Qt?

Boost.Signals2 and Qt are pretty cool libraries and do their jobs well.

This library is not meant to replace signals and slots, it focuses more on providing easy to use observable objects and expressions that can help with patterns like MVC and reactive programming.

Choose whichever library works best for your case; you can even choose them both (for example, have your models use this library and your views use Qt).