ObservableProperty 👀

A header-only C++ utility library for creating observable class properties. ObservableProperty allows classes to notify listeners of changes to their data members, making it easier to build reactive components in C++.

The main use case for this library is to facilitate data binding in MVVM-style architectures in C++. You can use ObservableProperty similarly to an event in C# or LiveData in Android.

If you want the callback to be called on a particular thread, you can subclass MutableObservableProperty. See LiveObservableProperty for how to do it in the JUCE C++ framework.

Installation

To use the library, you can put the include/ folder in your include path OR link against it in CMake:

target_link_libraries(MyProject PRIVATE wolfsound::observable_property)

Just #include <observable_property/ObservableProperty.hpp> and you're good to go!

The library uses boost-signals2 internally (bundled with this repo).

Usage

A minimal example:

#include <observable_property/ObservableProperty.hpp>

class Holder {
public:
  [[nodiscard]] ObservableProperty<int>& property() noexcept {
    return property_;
  }

  void incrementValue() { property_.setValue(property_.value() + 1); }

private:
  MutableObservableProperty<int> property_{0};
} holder;

const auto connection = holder.property().observe([&](const int& value) {
  // callback code
});

// Doesn't work although property() is public.
// holder.property().setValue(1);

// Tightly restricted API
holder.incrementValue();

You can use OBSERVABLE_PROPERTY macro to avoid boilerplate:

#include <observable_property/ObservableProperty.hpp>

class Holder {
public:
  Holder() : property_{0} {}

  OBSERVABLE_PROPERTY(property, int)

  void incrementValue() { property_.setValue(property_.value() + 1); }
} holder;

const auto connection = holder.property().observe([&](const int& value) {
  // callback code
});

// Doesn't work although property() is public.
// holder.property().setValue(1);

// Tightly restricted API
holder.incrementValue();

See tests in tests/ folder for more details.

License

For simplicity, this library is licensed under the Boost Software License, Version 1.0. See the LICENSE file for details.

Contributing

Contributions are welcome! Please feel free to submit issues or pull requests for any improvements or new features.