Getting the Feedback of an Action Server

[Beril-1]

Hello!

I would like to ask if there is a way to access feedback of an Action Server without sending a Goal ( without using SendGoal function.) I created a NewSimpleActionClient and I was trying to use actionproc.Messages function, but all returned values are empty. Is there a correct way to do it ? Thank you for help!

Cheers,
Beril

[aler9]

Hello, you can receive feedback at any time, without sending a goal, by subscribing to the dedicated action topic, that should be nameofaction/feedback. The tricky part consists in finding the right message type to use, that is an automatically generated message derived from an action, that should be generated in this way (most of the code is taken from actionclient.go:

package main

import (
    "fmt"
    "reflect"
    
    "github.com/aler9/goroslib"
    "github.com/aler9/goroslib/pkg/actionproc"
    "github.com/aler9/goroslib/pkg/msg"
)

type DoSomethingActionGoal struct {
    Input uint32
}

type DoSomethingActionResult struct {
    Output uint32
}

type DoSomethingActionFeedback struct {
    PercentComplete float32
}

type DoSomethingAction struct {
    msg.Package `ros:"shared_actions"`
    DoSomethingActionGoal
    DoSomethingActionResult
    DoSomethingActionFeedback
}

func main() {
    node, err := goroslib.NewNode(goroslib.NodeConf{
        Namespace:     "/myns",
        Name:          "goroslib-server",
        MasterAddress: "mymaster:11311",
    })
    if err != nil {
        panic(err)
    }
    defer node.Close()

    _, _, fbAction, err := actionproc.Messages(&DoSomethingActionGoal{})
    if err != nil {
        panic(err)
    }
    
    sub, err := goroslib.NewSubscriber(goroslib.SubscriberConf{
        Node:  node,
        Topic: "actionname/feedback",
        Callback: reflect.MakeFunc(
            reflect.FuncOf([]reflect.Type{reflect.PtrTo(reflect.TypeOf(fbAction))}, []reflect.Type{}, false),
            onFeedback,
        ).Interface(),
    })
    if err != nil {
        panic(err)
    }
    defer sub.Close()
    
    select {}
}

func onFeedback(in []reflect.Value) []reflect.Value {
    fbAction := in[0]

    reflect.ValueOf(onFeedback2).Call([]reflect.Value{
        fbAction.Elem().FieldByName("Feedback").Addr(),
    })

    return []reflect.Value{}
}

func onFeedback2(fb *DoSomethingActionFeedback) {
    fmt.Println("FEEDBACK", fb)
}