handleGoalResponse

Accept or reject new ROS 2 action goal and send status

Since R2023b

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Syntax

handleGoalResponse(server,goalStruct,goalStatus)

Description

handleGoalResponse(server,goalStruct,goalStatus) accepts or rejects a new action goal associated with the goal structure goalStruct that a client sent to the ROS 2 action server server, based on the specified goal acceptance status goalStatus. Use this function in the new goal reception callback function specified to the ReceiveGoalFcn property of the ros2actionserver object.

example

Examples

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Open Live Script

This example shows how to create a ROS 2 action server, connect an action client to it, receive a goal, and execute it.

Create a ROS 2 node.

node = ros2node("/node_1");

Set up an action server for calculating Fibbonacci sequence. Specify the goal execution, reception and cancel callbacks.

server = ros2actionserver(node,"/fibbonacci","example_interfaces/Fibonacci",ReceiveGoalFcn=@goalReceptionCB,...
                          ExecuteGoalFcn=@goalExecutionCB,CancelGoalFcn=@cancelGoalCB)
server = 
  ros2actionserver with properties:

          ActionName: '/fibbonacci'
          ActionType: 'example_interfaces/Fibonacci'
       MultiGoalMode: 'on'
      ExecuteGoalFcn: @goalExecutionCB
      ReceiveGoalFcn: @goalReceptionCB
       CancelGoalFcn: @cancelGoalCB
      GoalServiceQoS: 'History: keeplast, Depth: 10, Reliability: reliable, Durability: volatile, Deadline: Inf, Lifespan: Inf, Liveliness: automatic, Lease Duration: Inf'
    ResultServiceQoS: 'History: keeplast, Depth: 10, Reliability: reliable, Durability: volatile, Deadline: Inf, Lifespan: Inf, Liveliness: automatic, Lease Duration: Inf'
    CancelServiceQoS: 'History: keeplast, Depth: 10, Reliability: reliable, Durability: volatile, Deadline: Inf, Lifespan: Inf, Liveliness: automatic, Lease Duration: Inf'
    FeedbackTopicQoS: 'History: keeplast, Depth: 10, Reliability: reliable, Durability: volatile, Deadline: Inf, Lifespan: Inf, Liveliness: automatic, Lease Duration: Inf'
      StatusTopicQoS: 'History: keeplast, Depth: 1, Reliability: reliable, Durability: transientlocal, Deadline: Inf, Lifespan: Inf, Liveliness: automatic, Lease Duration: Inf'

Create an action client and specify a goal message to calculate the Fibbonacci sequence up to 10 terms past the first term 0.

client = ros2actionclient(node,"/fibbonacci","example_interfaces/Fibonacci");
waitForServer(client);
goalMsg = ros2message(client);
goalMsg.order = int32(10);

Send the goal. Use ros2ActionSendGoalOptions function to specify callback options when the client receives feedback and result messages from the server.

callbackOpts = ros2ActionSendGoalOptions(FeedbackFcn=@printFeedback,ResultFcn=@printResult);
goalHandle = sendGoal(client,goalMsg,callbackOpts);

Supporting Functions

goalReceptionCB is the goal reception callback that is triggered when the action server receives a new goal. Use the handleGoalResponse object function to accept or reject a new goal.

function goalReceptionCB(src,goalStruct)
    fprintf("[Server] Goal received, UUID: %s\n",goalStruct.goalUUID)
    if goalStruct.goal.order < 1
        % Reject Goal
        handleGoalResponse(src,goalStruct,'REJECT');
    else
        handleGoalResponse(src,goalStruct,'ACCEPT_AND_EXECUTE');
    end
end

goalExecutionCB is the goal execution callback that is triggered after a new goal is accepted and the server is ready to execute it. In this example, use goalExecutionCB to calculate the Fibonacci sequence for the number of terms specified in the goal message. First, check whether the client has preempted the goal using the isPreemptRequested object function. If not, continue goal execution and send periodic feedback to the client about the goal execution status.

function [result,success] = goalExecutionCB(src,goalStruct,defaultFeedbackMsg,defaultResultMsg)
    fprintf('[Server] Goal accepted and executing, UUID: %s\n', goalStruct.goalUUID);
    success = true;
    result = defaultResultMsg;
    feedback = defaultFeedbackMsg;
    feedback.sequence = int32([0;1]);
    for k=1:goalStruct.goal.order-1
        % Check that the client has not preempted the goal
        if isPreemptRequested(src,goalStruct)
            success = false;
            break
        end

        % Periodically send feedback to the client
        feedback.sequence = [feedback.sequence; int32(0)];
        feedback.sequence(end) = feedback.sequence(end-1) + feedback.sequence(end-2);
        sendFeedback(src,goalStruct,feedback);
    end

    if success
        result.sequence = feedback.sequence;
    end
end

cancelGoalCB is the cancel goal callback that is triggered after the server receives a cancel request from the client.

function cancelGoalCB(~,goalStruct)
    fprintf('[Server] Received request to cancel goal with UUID: %s\n', goalStruct.goalUUID);
end

printFeedback function is triggered when the client receives the feedback message from the server.

function printFeedback(goalHandle,resp)
    seq = resp.sequence;
    fprintf("[Client] Feedback: Fibonacci sequence for goal %s calculated currently: [", goalHandle.GoalUUID);
    for i=1:numel(seq)
        fprintf(" %d",seq(i));
    end
   fprintf(' ]\n');
end

printResult function is triggered when the client receives the result message from the server.

function printResult(goalHandle,resp)
    seq = resp.result.sequence;
    fprintf("[Client] Result: Fibonacci sequence for goal %s is: [", goalHandle.GoalUUID);
    for i=1:numel(seq)
        fprintf(" %d",seq(i));
    end
    fprintf(' ]\n');
end

Input Arguments

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ROS 2 action server, specified as a ros2actionserver object.

Structure containing the goal information, specified as a ROS 2 action goal structure. The new goal reception callback function in the ReceiveGoalFcn property of the ros2actionserver object automatically generates this structure as an input argument. The ROS 2 action goal structure contains these fields:

  • goal — Goal message structure

  • goalUUID — Unique ID of the goal

Goal acceptance status, specified as one of these options:

  • 'ACCEPT_AND_EXECUTE' — Accepts the goal for execution and sends the acceptance status to the client. If the ROS 2 action server is in multi-goal mode, the server puts the goal in the queue for execution. If the server is not in multi-goal mode, the server executes the goal immediately.

  • 'REJECT' — Rejects the goal and sends the rejection status to the client.

Extended Capabilities

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C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

Version History

Introduced in R2023b

See Also

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