ros2publisher

Publish messages on a topic

Description

Use the ros2publisher object to publish messages on a topic. When messages are published on that topic, ROS 2 nodes that subscribe to that topic receive those messages directly.

Creation

Syntax

pub = ros2publisher(node,topic)

pub = ros2publisher(node,topic,type)

pub = ros2publisher(___,Name,Value)

[pub,msg] = ros2publisher(___)

Description

pub = ros2publisher(node,topic) creates a publisher, pub, for a topic with name topic that already exists on the ROS 2 network. node is the ros2node object handle to which the publisher should attach. The publisher gets the topic message type from the network topic list.

Note

The topic must be on the network topic list.

pub = ros2publisher(node,topic,type) creates a publisher for a topic and adds that topic to the network topic list. If the topic list already contains a matching topic, pub will be added to the list of publishers for that topic.

pub = ros2publisher(___,Name,Value) specifies additional options using one or more name-value pair arguments. Specify name-value pair arguments after all other input arguments.

[pub,msg] = ros2publisher(___) returns a message, msg, that you can send with the publisher, pub. The message is initialized with default values. You can also get the ROS message using the ros2message function.

Input Arguments

node — ROS 2 node

node structure

A ros2node object on the network.

topic — Name of the published topic

string scalar | character vector

Name of the published topic, specified as a string scalar or character vector. If the topic does not exist, the object creates the topic using its associated message type.

This property is set at creating by the TopicName argument. The value cannot be changed after creation.

Example: "/chatter"

Data Types: char

type — Message type of published messages

string scalar | character vector

Message type of published messages, specified as a string scalar or character vector. This message type remains associated with the topic and must be used for new messages published.

This property is set at creation by the MessageType argument. The value cannot be changed after creation.

Example: "std_msgs/String"

Data Types: char

Name-Value Arguments

Specify optional pairs of arguments as Name1=Value1,...,NameN=ValueN, where Name is the argument name and Value is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.

Before R2021a, use commas to separate each name and value, and enclose Name in quotes.

History — Mode of storing messages in the queue

"keeplast" (default) | "keepall"

Determines the mode of storing messages in the queue. The queued messages will be sent to late-joining subscribers. If the queue fills with messages waiting to be processed, then old messages will be dropped to make room for new. If set to "keeplast", the queue stores the number of messages set by the Depth property. If set to "keepall", the queue stores all messages up to the resource limits of MATLAB^®.

Data Types: double

Depth — Size of the message queue

positive integer

Number of messages stored in the message queue when History is set to "keeplast".

Example: 42

Data Types: double

Reliability — Delivery guarantee of messages

"reliable" (default) | "besteffort"

Affects the guarantee of message delivery. If "reliable", then delivery is guaranteed, but may retry multiple times. If "besteffort", then delivery is attempt, but retried.

Example: "reliable"

Data Types: char | string

Durability — Persistence of messages

"volatile" (default) | "transientlocal"

Affects persistence of messages in publishers, which allows late-joining subscribers to receive the number of old messages specified by Depth. If "volatile", then messages do not persist. If "transientlocal", then publisher will persist most recent messages.

Example: "volatile"

Data Types: char | string

Properties

TopicName — Name of the published topic

string scalar | character vector

Name of the published topic, specified as a string scalar or character vector. If the topic does not exist, the object creates the topic using its associated message type.

This property is set at creating by the TopicName argument. The value cannot be changed after creation.

Example: "/chatter"

Data Types: char

MessageType — Message type of published messages

string scalar | character vector

Message type of published messages, specified as a string scalar or character vector. This message type remains associated with the topic and must be used for new messages published.

This property is set at creation by the MessageType argument. The value cannot be changed after creation.

Example: "std_msgs/String"

Data Types: char

History — Message queue mode

"keeplast" (default) | "keepall"

This property is read-only.

Determines the mode of storing messages in the queue. The queued messages will be sent to late-joining subscribers. If the queue fills with messages waiting to be processed, then old messages will be dropped to make room for new. When set to "keeplast", the queue stores the number of messages set by the Depth property. Otherwise, when set to "keepall", the queue stores all messages up to the resource limits of MATLAB.

Example: "keeplast"

Data Types: char | string

Depth — Size of the message queue

positive integer

This property is read-only.

Number of messages stored in the message queue when History is set to "keeplast".

Example: 42

Data Types: double

Reliability — Delivery guarantee of messages

"reliable" (default) | "besteffort"

This property is read-only.

Affects the guarantee of message delivery. If "reliable", then delivery is guaranteed, but may retry multiple times. If "besteffort", then delivery is attempt, but retried.

Example: "reliable"

Data Types: char | string

Durability — Persistence of messages

"volatile" (default) | "transientlocal"

This property is read-only.

Affects persistence of messages in publishers, which allows late-joining subscribers to receive the number of old messages specified by Depth. If "volatile", then messages do not persist. If "transientlocal", then publisher will persist most recent messages.

Example: "volatile"

Data Types: char | string

Object Functions

ros2message	Create ROS 2 message structures
send	Publish ROS 2 message to topic

Examples

Create an Empty ROS 2 Message

Create a ROS 2 node.

node = ros2node("/node_1");

Create publisher and message.

chatPub = ros2publisher(node,"/chatter","std_msgs/String")

chatPub = 
  ros2publisher with properties:

      TopicName: '/chatter'
    MessageType: 'std_msgs/String'
        History: 'keeplast'
          Depth: 10
    Reliability: 'reliable'
     Durability: 'volatile'

msg = ros2message(chatPub)

msg = struct with fields:
    MessageType: 'std_msgs/String'
           data: ''

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

• MessageType argument must be specified.

• ros2publisher(___) does not return a message, msg, that you can send with the publisher, pub. You can get the ROS message using the ros2message function.

Version History

Introduced in R2019b