Translating a message to a payload in Scala / Grpc

Question

After days of trying and failed, finally I have succeed in implementing both Grpc and Gatling plugins into one project (embarrassingly long time), now I am looking into phiSgr example (again, sorry for this), and I see there is a part as this:

message GreetRequest {
    string username = 1;
    string name = 2;
}

and in GrpcExample.scala, he "translate it":

  val greetPayload: Expression[GreetRequest] = GreetRequest(name = "World").updateExpr(
    _.username :~ $("username")
  )

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So I just want to know the procedure to translate this chunk:

message Device {
   string id = 1[(google.api.field_behavior) = REQUIRED]
}

message StartPairingRequest {
   Device device = 1 [(google.api.field_behavior) = REQUIRED]
}

With a body message when I do request

{
   "Device": {
       "id": "random text"
   }
}

What I have tried to do in .scala file:

val greetPayload: Expression[StartPairingRequest] = StartPairingRequest(device = " "theBody" = "random text" ").updateExpr(
_.device:~$("device")
)

it seems that my implementation is not right, so I would wish to learn more about this "translating" procedure, please help.

Answer 1

The extension function updateExpr and the operator :~ are used to construct dynamic payload with the virtual user's Session.

Using them requires knowing a concept called lens, which is used in ScalaPB.

Those who lack the prior knowledge are strongly recommended to use the Kotlin binding and write your load tests in Kotlin/Java.

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However the payload described in this question has no dynamic value, and can be constructed simply as:

StartPairingRequest(Device("random text"))