Generated ROS Message Plugin

Source code generated by cx_ros_comm_gen.

Given the package (e.g., std_msgs) and msg_name (e.g., String), this document uses the following abbreviations:

• PkgCamel: CamelCase of package (e.g., StdMsgs)

• MsgCamel: CamelCase of msg_name (e.g., String)

• pkg-kebab: kebab-case of package (e.g., std-msgs)

• msg-kebab: kebab-case of msg_name (e.g., string)

Plugin Class

cx::CXPkgCamelMsgCamelPlugin

(e.g., cx::CXStdMsgsStringPlugin)

Configuration

This plugin has no specific configuration.

Features

Facts

; Asserted by the respective create-subscription function.
; Retracted by the respective destroy-subscription function.
(<pkg-kebab>-<msg-kebab>-subscription (topic ?topic-name-string))

; Asserted by the respective create-publisher function.
; Retracted by the respective destroy-publisher function.
(<pkg-kebab>-<msg-kebab>-publisher (topic ?topic-name-string))

; Asserted by the callback of a subscriber whenever a message arrives.
; Process the message and then call destroy-message before retracting!
(<pkg-kebab>-<msg-kebab>-message (topic ?topic-name-string) (msg-ptr ?msg-ptr))

Functions

; Create and destroy publishers and subscriptions.
(<pkg-kebab>-<msg-kebab>-create-publisher ?topic-name)
(<pkg-kebab>-<msg-kebab>-destroy-publisher ?topic-name)
(<pkg-kebab>-<msg-kebab>-create-subscription ?topic-name)
(<pkg-kebab>-<msg-kebab>-destroy-subscription ?topic-name)

; Publish a given message over a topic.
; Requires the publisher to be created first using create-publisher.
(<pkg-kebab>-<msg-kebab>-publish ?msg-ptr ?topic-name)

; Create a message and return a pointer to it
(bind ?msg-ptr (<pkg-kebab>-<msg-kebab>-create-message))
; Destroy a message, call this after publishing a message or processing an incoming message to prevent it from staying in memory.
(<pkg-kebab>-<msg-kebab>-destroy-message ?msg-ptr)

; Populate the field of a message.
; If the field is a message, then pass a pointer to that message (by using that respective messages bindings).
(<pkg-kebab>-<msg-kebab>-set-field ?msg-ptr ?field-name ?field-value)

; Retrieve a field of a message.
; If the field is a message, then a pointer is returned that can only be processed by using that respective messages bindings.
(<pkg-kebab>-<msg-kebab>-get-field ?msg-ptr ?field-name)

Usage Example

A minimal working example is provided by the cx_bringup package. Run it via:

ros2 launch cx_bringup cx_launch.py manager_config:=plugin_examples/string_msg.yaml

It creates a std_msgs/msg/String subscription on topic /ros_cx_in and prints out any text send over it. Additionally, it creates a publisher on /ros_cx_out that publishes Hello World whenever something is received over the /ros_cx_in topic.

Configuration

File cx_bringup/params/plugin_examples/string_msg.yaml.

clips_manager:
  ros__parameters:
    environments: ["cx_string_msg"]
    cx_string_msg:
      plugins: ["executive", "string_msg", "files"]
      log_clips_to_file: true
      watch: ["facts", "rules"]

    executive:
      plugin: "cx::ExecutivePlugin"
      publish_on_refresh: false
      assert_time: true
      refresh_rate: 10
    string_msg:
      plugin: "cx::CXStdMsgsStringPlugin"
    files:
      plugin: "cx::FileLoadPlugin"
      pkg_share_dirs: ["cx_bringup"]
      load: [
        "clips/plugin_examples/string-msg.clp"]

Code

File cx_bringup/clips/plugin_examples/string-msg.clp.

(defrule string-pub-sub-init
" Create a simple publisher and subscriber using the generated bindings. "
  (not (std-msgs-string-subscription (topic "ros_cx_in")))
  (not (std-msgs-string-publisher (topic "ros_cx_out")))
=>
  (std-msgs-string-create-publisher "ros_cx_out")
  (printout info "Created publisher for /ros_cx_out" crlf)
  (std-msgs-string-create-subscription "ros_cx_in")
  (printout info "Listening for String messages on /ros_cx_in" crlf)
)

(defrule string-publisher-recv-and-answer
" React to incoming messages and answer (on a different topic) "
  (std-msgs-string-subscription (topic ?sub))
  ?msg-f <- (std-msgs-string-message (topic ?sub) (msg-ptr ?inc-msg))
  (std-msgs-string-publisher (topic ?pub))
  =>
  ; fetch the content of the message and print it
  (bind ?recv (std-msgs-string-get-field ?inc-msg "data"))
  (printout blue "Recieved via " ?sub " :" ?recv crlf)
  ; make sure to actually destroy the message to free heap-allocated memory for it, once the message is processed and can be removed
  (std-msgs-string-destroy-message ?inc-msg)
  (retract ?msg-f)

  ; example of how to create and send a new message
  (printout green "Sending Hello World Message in response!" crlf)
  (bind ?msg (std-msgs-string-create-message))
  (std-msgs-string-set-field ?msg "data" "Hello world!")
  (std-msgs-string-publish ?msg ?pub)
  ; destroy the msg after usage to free up the memory
  (std-msgs-string-destroy-message ?msg)
)

(defrule string-msg-pub-sub-finalize
" Delete the subscription and publisher on executive finalize. "
  (executive-finalize)
  (std-msgs-string-subscription (topic ?sub))
  (std-msgs-string-publisher (topic ?pub))
=>
  (printout debug "Destroying subscription " ?sub crlf)
  (printout debug "Destroying publisher " ?pub crlf)
  (std-msgs-string-destroy-subscription ?sub)
  (std-msgs-string-destroy-publisher ?pub)
)

(defrule ros-msgs-message-cleanup
" Delete any incoming msg on executive finalize. "
  (executive-finalize)
  ?msg-f <- (std-msgs-string-message (msg-ptr ?ptr))
=>
  (std-msgs-string-destroy-message ?ptr)
  (retract ?msg-f)
)