Example:

Build the node

 mkdir colcon_ws
 mkdir colcon_ws/src
 cd colcon_ws/src
 git clone https://github.com/picknikrobotics/generate_parameter_library.git
 cd ..
 colcon build

Run the C++ node

source install/setup.bash
ros2 run generate_parameter_library_example test_node --ros-args --params-file src/generate_parameter_library/example/config/implementation.yaml

You should see an output like this: [INFO] [1656018676.015816509] [admittance_controller]: Control frame is: 'ee_link'

ROS 2 CLI

Run the following:

ros2 param list

You should see:

/admittance_controller:
  admittance.damping_ratio
  admittance.mass
  admittance.selected_axes
  admittance.stiffness
  chainable_command_interfaces
  command_interfaces
  control.frame.external
  control.frame.id
  enable_parameter_update_without_reactivation
  fixed_array
  fixed_string
  fixed_string_no_default
  fixed_world_frame.frame.external
  fixed_world_frame.frame.id
  ft_sensor.filter_coefficient
  ft_sensor.frame.external
  ft_sensor.frame.id
  ft_sensor.name
  gravity_compensation.CoG.force
  gravity_compensation.CoG.pos
  gravity_compensation.frame.external
  gravity_compensation.frame.id
  interpolation_mode
  joints
  kinematics.alpha
  kinematics.base
  kinematics.group_name
  kinematics.plugin_name
  kinematics.plugin_package
  kinematics.tip
  one_number
  pid.elbow_joint.d
  pid.elbow_joint.i
  pid.elbow_joint.p
  pid.rate
  pid.shoulder_lift_joint.d
  pid.shoulder_lift_joint.i
  pid.shoulder_lift_joint.p
  pid.shoulder_pan_joint.d
  pid.shoulder_pan_joint.i
  pid.shoulder_pan_joint.p
  pid.wrist_1_joint.d
  pid.wrist_1_joint.i
  pid.wrist_1_joint.p
  pid.wrist_2_joint.d
  pid.wrist_2_joint.i
  pid.wrist_2_joint.p
  pid.wrist_3_joint.d
  pid.wrist_3_joint.i
  pid.wrist_3_joint.p
  qos_overrides./parameter_events.publisher.depth
  qos_overrides./parameter_events.publisher.durability
  qos_overrides./parameter_events.publisher.history
  qos_overrides./parameter_events.publisher.reliability
  scientific_notation_num
  state_interfaces
  three_numbers
  three_numbers_of_five
  use_feedforward_commanded_input
  use_sim_time
  

All parameter are automatically declared and callbacks are setup by default. You can set a parameter by typing:

ros2 param set /admittance_controller control.frame.id new_frame

You should see:

[INFO] [1656019001.515820371] [admittance_controller]: New control frame parameter is: 'new_frame'

Congratulations, you updated the parameter!

If you try to set a parameter that is read only, you will get an error. Running the following

ros2 param set /admittance_controller command_interfaces ["velocity"]

will result in the error

Setting parameter failed: parameter 'command_interfaces' cannot be set because it is read-only

Running the following

ros2 param describe /admittance_controller admittance.damping_ratio

will show a parameter’s description

 Parameter name: admittance.damping_ratio
  Type: double array
  Description: specifies damping ratio values for x, y, z, rx, ry, and rz used in the admittance calculation. The values are calculated as damping can be used instead: zeta = D / (2 * sqrt( M * S ))
  Constraints:
    Min value: 0.1
    Max value: 10.0

If you try to set a value out of the specified bounds,

ros2 param set /admittance_controller admittance.damping_ratio [-10.0,-10.0,-10.0,-10.0,-10.0,-10.0]

you will get the error

Setting parameter failed: Value -10.0 in parameter 'admittance.damping_ratio' must be within bounds [0.1, 10.0]

If you try to set a vector parameter with the wrong length,

ros2 param set /admittance_controller admittance.damping_ratio [1.0,1.0,1.0]

you will get the error

Setting parameter failed: Length of parameter 'admittance.damping_ratio' is 3 but must be equal to 6

If you try to load a yaml file with missing required parameters

ros2 run generate_parameter_library_example test_node --ros-args --params-file src/generate_parameter_library/example/config/missing_required.yaml

you will get the error

terminate called after throwing an instance of 'rclcpp::exceptions::ParameterUninitializedException'
  what():  parameter 'fixed_string_no_default' is not initialized
[ros2run]: Aborted

Changelog for package generate_parameter_library_example

0.3.9 (2024-10-27)

• Add "additional_constraints" support (#221)
• Use int64_t instead of int for parameter integer range, fixes #199 (#214)
• Add Non-Blocking try_get_params Function for Real-Time Control Systems (#205)
• Drop yaml brackets for consistency and readability (#203)
• Contributors: Auguste Bourgois, David Revay, KentaKato, Tim Clephas

0.3.8 (2024-03-27)

• Restore functionality for mapped params with no struct name ([#185 <https://github.com/PickNikRobotics/generate_parameter_library/issues/185>_]{.title-ref})
• Fix newline issue (#176)
  • fix new line rendering for Python
• Support nested mapped parameters (#166)
• Contributors: Paul Gesel, Sebastian Castro

0.3.7 (2024-01-12)

• Split example/README.md into C++ and Python version; updated content (#138)
• Contributors: chriseichmann

0.3.6 (2023-07-31)

0.3.5 (2023-07-28)

• Remove documentation of deprecated validator functions (#135)
• Contributors: Tyler Weaver

0.3.4 (2023-07-24)

• Add Python support for generate_parameter_library (#110) Co-authored-by: Tyler Weaver <<tyler@picknik.ai>>
• Contributors: Paul Gesel

0.3.3 (2023-04-13)

0.3.2 (2023-04-12)

• Populate Range Constraints in Parameter Descriptors from Validation Functions (#103)
• Mark deprecated rsl method and propose alternative in the docs. (#102)
• Contributors: Chance Cardona, Dr. Denis

0.3.1 (2023-02-01)

• Make it easy for users to override (#92)
• Contributors: Tyler Weaver

0.3.0 (2022-11-15)

• Migrate from parameter_traits to RSL (take 2) (#91)
• Contributors: Tyler Weaver

0.2.8 (2022-11-03)

0.2.7 (2022-10-28)

• Standardize cmake (#79)
• Contributors: Tyler Weaver

0.2.6 (2022-09-28)

0.2.5 (2022-09-20)

• 🈵 Support use of '_' in mapped parameters. (#68)
• Component node example (#60)
• Update README for example (#63)
• 🚀 Add cmake macros for using tests with example yaml files. 🤖 (#57) Co-authored-by: Tyler Weaver <<maybe@tylerjw.dev>>
• Fix example parameters (#54)
• Contributors: Denis Štogl, Paul Gesel, Tyler Weaver

0.2.4 (2022-08-19)

• INTEGER type (#53)
• 0.2.3
• Contributors: Tyler Weaver

0.2.3 (2022-08-05)

0.2.2 (2022-08-03)

0.2.1 (2022-08-02)

• Fix scientific notation (#46)
• Contributors: Paul Gesel

0.2.0 (2022-08-01)

• Create stack allocated struct (#45)
• Fixed length arrays (#44)
• Fixed size string no default bug (#43)
• static OK to fix ODR errors (#41)
• Change package name (#40)
• parameter validators interface library (#32)
• Validate fixed length Strings (#33)
• Fixed size strings (#29)
• Contributors: Paul Gesel, Tyler Weaver

0.1.0 (2022-07-27)

• Example usage of generate_parameter_library.
• Contributors: Paul Gesel, Tyler Weaver