rosmessage

Create a ROS message as a structure with the std_msgs/String message type.

strMsg = rosmessage("std_msgs/String","DataFormat","struct")

strMsg = struct with fields:
    MessageType: 'std_msgs/String'
           Data: ''

Start ROS master.

rosinit

Launching ROS Core...
Done in 0.82557 seconds.
Initializing ROS master on http://172.20.148.53:50298.
Initializing global node /matlab_global_node_39153 with NodeURI http://dcc867993glnxa64:39767/ and MasterURI http://localhost:50298.

Create publisher for the /chatter topic with the std_msgs/String message type. Set the "DataFormat" name-value argument to structure ROS messages.

chatpub = rospublisher("/chatter","std_msgs/String","DataFormat","struct");

Create a message to send. Specify the Data property with a character vector.

msg = rosmessage(chatpub);
msg.Data = 'test phrase';

Send the message via the publisher.

send(chatpub,msg);

Shut down the ROS network.

rosshutdown

Shutting down global node /matlab_global_node_39153 with NodeURI http://dcc867993glnxa64:39767/ and MasterURI http://localhost:50298.
Shutting down ROS master on http://172.20.148.53:50298.

You can create an structure array to store multiple messages. The array is indexable, similar to any other array. You can modify properties of each object or access specific properties from each element using dot notation.

Create an array of two messages. Specify the DataFormat name-value argument to use structures for ROS messages.

blankMsg = rosmessage("std_msgs/String","DataFormat","struct")

blankMsg = struct with fields:
    MessageType: 'std_msgs/String'
           Data: ''

msgArray = [blankMsg blankMsg]

msgArray=1×2 struct array with fields:
    MessageType
    Data

Assign data to individual message fields in the array.

msgArray(1).Data = 'Some string'; 
msgArray(2).Data = 'Other string';

Read all the Data fields from the messages into a cell array.

allData = {msgArray.Data}

allData = 1x2 cell
    {'Some string'}    {'Other string'}

To preallocate an array using ROS messages as objects, use the arrayfun or cellfun functions instead of repmat. These functions properly create object or cell arrays for handle classes.

Note: In a future release, ROS message objects will be removed. To use ROS messages as structures and utilize structure arrays, specify the DataFormat name-value pair when calling the rosmessage function.

Preallocate an object array of ROS messages.

msgArray = arrayfun(@(~) rosmessage("std_msgs/String"),zeros(1,50));

Preallocate a cell array of ROS messages.

msgCell = cellfun(@(~) rosmessage("std_msgs/String"),cell(1,50),"UniformOutput",false);