RxROS

Introduction

RxROS is new API for ROS based on the paradigm of reactive programming. Reactive programming is an alternative to callback-based programming for implementing concurrent message passing systems that emphasizes explicit data flow over control flow. It makes the message flow and transformations of messages easy to capture in one place. It eliminates problems with deadlocks and understanding how callbacks interact. It helps you to make your nodes functional, concise, and testable. RxROS aspires to the slogan ‘concurrency made easy’.

Contents

• RxROS
  • Introduction
  • Setup and installation
    • RxROS
  • Acknowledgements
  • Example packages
  • RxROS API
    • Creating a RxROS Node
      • Example
    • Parameters
      • Syntax
      • Example
    • Logging
      • Syntax
      • Example
    • Observables
      • Observable from a Topic
        • Syntax
        • Example
      • Observable from a transform listener
        • Syntax
      • Observable from a Linux device
        • Syntax
        • Example
      • Observable from a Yaml file
        • Syntax
        • Example
    • Operators
      • Publish to Topic
        • Syntax:
        • Example:
      • Send Transform
        • Syntax:
      • Call Service
        • Syntax:
      • Sample with Frequency
        • Syntax:
        • Example:
  • Example 1: A Keyboard Publisher
  • Example 2: A Velocity Publisher

Setup and installation

In order to make use of this software you must install one of the following ROS distributions on your computer:

• ROS Melodic Morenia, or
• ROS Kinetic Kame

RxROS

RxROS is installed using the following command (in Ubuntu and Debian, for ROS Melodic and Kinetic):

# for ROS Kinetic replace 'melodic' with 'kinetic'
sudo apt install ros-melodic-rxros

To start using RxROS create a package in your Catkin workspace which depends on the rxros package:

# make sure to source the correct version of ROS. If your using
# Kinetic, replace 'melodic' with 'kinetic' in the following command
source /opt/ros/melodic/setup.bash

# create a workspace (skip if you already have a workspace)
mkdir -p ~/my_ws/src
cd ~/my_ws/src

# create your package 'my_pkg' which has 'rxros' as a dependency
catkin_create_pkg my_pkg std_msgs rxros

# create the files you need in your new package ...

# build your workspace
cd ~/my_ws
catkin_make

A typical RxROS program should include the rxros/rxros.h header file as shown in the following code:

```cpp #include <rxros/rxros.h> // … add your code here

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