delete

Remove ros2bagwriter object from memory

Syntax

delete(bagwriter)

Description

delete(bagwriter) removes the ros2bagwriter object from memory. The function closes the opened ROS 2 bag file before deleting the object.

If multiple references to the ros2bagwriter object exist in the workspace, deleting the ros2bagwriter object invalidates the remaining reference. Use the clear command to delete the remaining references to the object from the workspace.

Note

The ros2bagwriter object locks the created bag file. Delete and clear the ros2bagwriter object to use the ROS 2 bag file.

Examples

Write Log Using ros2bagwriter Object by Reading Messages from ROS 2 Bag File

Extract the zip file that contains the ROS 2 bag log file and specify the full path to the log folder.

unzip('ros2_netwrk_bag.zip');
folderPath = fullfile(pwd,'ros2_netwrk_bag');

Get all the information from the ROS 2 bag log file.

bag2info = ros2("bag","info",folderPath);

Create a ros2bagreader object that contains all messages in the log file.

bag = ros2bagreader(folderPath);
bag.AvailableTopics

ans=4×3 table
                NumMessages         MessageType                                                   MessageDefinition                                           
                ___________    _____________________    ______________________________________________________________________________________________________

    /clock       1.607e+05     rosgraph_msgs/Clock      {'%...'                                                                                              }
    /cmd_vel             3     geometry_msgs/Twist      {'...'                                                                                               }
    /odom             5275     nav_msgs/Odometry        {'% The pose in this message should be specified in the coordinate frame given by header.frame_id...'}
    /scan              892     sensor_msgs/LaserScan    {'%...'                                                                                              }

Select a subset of the messages, by applying filters to the topic and timestamp.

start = bag.StartTime;
odomBagSel = select(bag,"Time",[start start + 30e+09],"Topic","/odom")

odomBagSel = 
  ros2bagreader with properties:

           FilePath: '/tmp/Bdoc22b_2134332_1954357/tpdf3c6620/ros-ex95368813/ros2_netwrk_bag/ros2_netwrk_bag.db3'
          StartTime: 1601984883976047597
            EndTime: 1601984913775044431
    AvailableTopics: [1x3 table]
        MessageList: [801x3 table]
        NumMessages: 801

Get the messages in the selection.

odomMsgs = readMessages(odomBagSel);

Retrieve the list of timestamps from the topic. Convert the list to values with the double data type.

timestamps = odomBagSel.MessageList.Time;
timestamps_double = num2cell(double(timestamps)/1e+09);

Create a ros2bagwriter object and a ROS 2 bag file in the specified folder.

bagwriter = ros2bagwriter("myRos2bag");

Write the messages related to the topic '/odom' to the ROS 2 bag file.

write(bagwriter,"/odom",timestamps_double,odomMsgs)

Close the bag file, remove the ros2bagwriter object from memory, and clear the associated object.

delete(bagwriter)
clear bagwriter

Load the new ROS 2 bag log file.

bagOdom = ros2bagreader("myRos2bag");

Retrieve messages from the ROS 2 bag log file.

msgs = readMessages(bagOdom);

Plot the coordinates for the messages in the ROS 2 bag log file.

Remove the myRos2bag file and the ros2_netwrk_bag file from memory to run the example again.

plot(cellfun(@(msg) msg.pose.pose.position.x,msgs),cellfun(@(msg) msg.twist.twist.angular.z,msgs))

Create Single Log and Write to ROS 2 Bag File

Create a ros2bagwriter object and a ROS 2 bag file in the specified folder.

bagwriter = ros2bagwriter("myRos2bag");

Write a single log to the ROS 2 bag file.

topic = "/odom";
message = ros2message("nav_msgs/Odometry");
timestamp = ros2time(1.6170e+09);
write(bagwriter,topic,timestamp,message)

Close the bag file, remove the ros2bagwriter object from memory, and clear the associated object.

delete(bagwriter)
clear bagwriter

Create Multiple Logs and Write to ROS 2 Bag File

Create a ros2bagwriter object and a ROS 2 bag file in the specified folder. Specify the cache size for each message.

bagwriter = ros2bagwriter("bag_files/my_bag_file",CacheSize=1500);

Write multiple logs to the ROS 2 bag file.

message1 = ros2message("nav_msgs/Odometry");
message2 = ros2message("geometry_msgs/Twist");
message3 = ros2message("sensor_msgs/Image");
write(bagwriter, ...
      ["/odom","cmd_vel","/camera/rgb/image_raw"], ...
      {ros2time(1.6160e+09),ros2time(1.6170e+09),ros2time(1.6180e+09)}, ...
      {message1,message2,message3})

Close the bag file, remove the ros2bagwriter object from memory, and clear the associated object.

delete(bagwriter)
clear bagwriter

Create Multiple Logs for Same Topic and Write to ROS 2 Bag File

Create a ros2bagwriter object and a ROS 2 bag file in the specified folder.

bagwriter = ros2bagwriter("myBag");

Write multiple logs for the same topic to the ROS 2 bag file.

pointMsg1 = ros2message("geometry_msgs/Point");
pointMsg1.x = 1;
pointMsg2 = ros2message("geometry_msgs/Point");
pointMsg2.x = 2;
pointMsg3 = ros2message("geometry_msgs/Point");
pointMsg3.x = 3;
write(bagwriter, ...
      "/point", ...
      {1.6190e+09, 1.6200e+09,1.6210e+09}, ...
      {pointMsg1,pointMsg2,pointMsg3})

Close the bag file, remove the ros2bagwriter object from memory, and clear the associated object.

delete(bagwriter)
clear bagwriter

Input Arguments

bagwriter — ROS 2 log file writer

ros2bagwriter object

ROS 2 log file writer, specified as a ros2bagwriter object.

Version History

Introduced in R2022b