rtt_rosparam

RTT ROSParam

This package provides an RTT service and service-requester for associating RTT component properties with ROS parameters.

Design

This RTT service enables both setting/getting individual RTT properties of a given RTT component to/from the ROS parameter server, as well as setting/getting all properties of a component simultaneously. The operations map directly onto operations in the roscpp library, except they only store the retrieved values in RTT properties of the given component.

Using this service requires that the RTT properties of a given component match the names of their associated ROS parameters, modulo the namespace resolution policy (see below).

Usage

Service Interface

Constants (name resolution policies):

• RELATIVE Relative resolution: "name" -> "name"
• ABSOLUTE Absolute resolution: "name" -> "/name"
• PRIVATE Private resolution: "name" -> "~name"
• COMPONENT Component resolution: "name" -> "~COMPONENT_NAME/name"

Operations (getting/setting params)

Operations for getting all properties

• getAll() or getAllComponentPrivate() Attempt to get all properties of this component (and its sub-services) from the ROS parameter server in the COMPONENT namespace.
• getAllRelative() Attempt to get all properties of this component (and its sub-services) from the ROS parameter server in the relative namespace.
• getAllAbsolute() Attempt to get all properties of this component (and its sub-services) from the ROS parameter server in the absolute namespace.
• getAllPrivate() Attempt to get all properties of this component (and its sub-services) from the ROS parameter server in the node's private namespace.

Operations for setting all properties

• setAll() or setAllComponentPrivate() Stores all properties of this component (and its sub-services) on the ROS parameter server from the similarly-named property in the COMPONENT's private namespace.
• setAllRelative() Stores all properties of this component (and its sub-services) on the ROS parameter server from the similarly-named property in the relative namespace.
• setAllAbsolute() Stores all properties of this component (and its sub-services) on the ROS parameter server from the similarly-named property in the absolute namespace.
• setAllPrivate() Stores all properties of this component (and its sub-services) on the ROS parameter server from the similarly-named property in the node's private namespace.

Operations for getting single properties

• getParam(ros_name, rtt_name) Get the ROS param ros_name and store it in the RTT property rtt_name. Use leaders like ~ and / for private and absolute resolution.
• get(name ,policy) Attempt to get the property named name (or populates the properties of a named RTT sub-service) from the ROS parameter namespace specified by policy.
• getRelative(name)
• getAbsolute(name)
• getPrivate(name)
• getComponentPrivate(name)

Operations for setting single properties

• setParam(ros_name, rtt_name) Set the ROS param ros_name from the value in the RTT property rtt_name*. Use leaders like ~ and / for private and absolute resolution.
• set(name, policy) Attempt to set the property named name (or stores the properties of a named RTT sub-service) in the ROS parameter namespace specified by policy.
• setRelative(name)
• setAbsolute(name)
• setPrivate(name)
• setComponentPrivate(name)

Operations to create properties linked to a ROS param

The following operations of the rosparam service can be used to create properties in the owner component that link to ROS parameters. When the properties are evaluate()-d through get() or set(), the ROS parameter server is queried.

IMPORTANT Setting or getting the value of a ROS parameter through a property is a non real-time safe operation and therefore it shouldn't be used from within a real-time component.

• addRosParamProperty_type_(name) Adds a property of type _type_ with name name to the owning task context which is linked to the ROS parameter with the same name in a Relative namespace resolution context.
• addRosParamProperty_type_Relative(name) Adds a property of type _type_ with name name to the owning task context which is linked to the ROS parameter with the same name in a Relative namespace resolution context.
• addRosParamProperty_type_Absolute(name) Adds a property of type _type_ with name name to the owning task context which is linked to the ROS parameter with the same name in a Absolute namespace resolution context.
• addRosParamProperty_type_Private(name) Adds a property of type _type_ with name name to the owning task context which is linked to the ROS parameter with the same name in a Private namespace resolution context.
• addRosParamProperty_type_ComponentPrivate(name) Adds a property of type _type_ with name name to the owning task context which is linked to the ROS parameter with the same name in a ComponentPrivate namespace resolution context.
• addRosParamProperty_type_ComponentAbsolute(name) Adds a property of type _type_ with name name to the owning task context which is linked to the ROS parameter with the same name in a ComponentAbsolute namespace resolution context.
• addRosParamProperty_type_ComponentRelative(name) Adds a property of type _type_ with name name to the owning task context which is linked to the ROS parameter with the same name in a ComponentRelative namespace resolution context.

Scripting Interface

Components which were never meant to be used with ROS parameters can have their properties set from the ROS parameter server through the scripting interface:

// Import packages
import("rtt_ros")
ros.import("rtt_rosparam")

// Create your components ...
laodService("my_component","rosparam")

// Try to get all parameters from the component namespace "~my_component/..."
my_component.rosparam.getAll()

// Try to get the "robot_description" property from the absolute namespace "/robot_description"
my_component.rosparam.getAbsolute("robot_description")
// Alternatively:
my_component.rosparam.get("robot_description",my_component.rosparam.ABSOLUTE)

// Create a property linked to a ROS parameter
my_component.rosparam.addRosParamPropertyDouble("parameter_double")
my_component.rosparam.addRosParamPropertyStringAbsolute("robot_name")

// Change ROS parameter through Property
my_component.parameter_double = 3.1
my_component.parameter_double = other_component.other_double
var double my_double
my_component.parameter_double = my_double

C++ Interface

If your component is designed to be used with ROS parameters, you can also easily access the rosparam service from C++ using an RTT ServiceRequester.

For example, a simple component which gets the "robot_description" ROS param from the global namespace ("/robot_description") and the "publish_period" ROS param from the node's private namespace ("~publish_period") would look something like the following:

// Include the service requester interface
#include <rtt_rosparam/rosparam.h>


class MyComponent : public RTT::TaskContext {
  private:
    // Storage for RTT properties
    std::string robot_description_;
    double publish_period_;

  public:
    MyComponent::MyComponent(std::string &name) : RTT::TaskContext(name) {
      // Add some properties
      this->addProperty("robot_description",robot_description_);
      this->addProperty("publish_period",publish_period_);
      // Get the rosparam service requester
      boost::shared_ptr<rtt_rosparam::ROSParam> rosparam =
          this->getProvider<rtt_rosparam::ROSParam>("rosparam");
      if(rosparam) {
        // Add some more properties linked to ROS parameters
        rosparam->addRosParamPropertyDouble("parameter_double");
      }
    }

    // ... 

    bool configureHook() {
      bool all_params_found = true;

      // Get the rosparam service requester
      boost::shared_ptr<rtt_rosparam::ROSParam> rosparam =
          this->getProvider<rtt_rosparam::ROSParam>("rosparam");

      // Get the parameters
      if(rosparam) {
        // Get the ROS parameter "/robot_description"
        all_params_found &= rosparam->getAbsolute("robot_description");

        // Get the ROS parameter "~publish_period"
        all_params_found &= rosparam->getPrivate("publish_priod");

        // Evaluate parameter (updates from)
        this->getProperty("parameter_double")->value();
      }
      
      return all_params_found;
    }

    // ...
}

See the API documentation for more information.