How to set some mutual exclusion objects in a message

[Ann Lin]

Hello:

I'm a Typescript developer and trying to use protobuf between Typescript and Python.

I have to translate several Typescripts interface below to proto3 messages:

```typescript

enum CommandType {

    'Run',

    'Sleep',

    'Read'

}

interface RunCommand {

    commandType: CommandType.Run;

    destination: string;

}

interface SleepCommand {

    commandType: CommandType.Sleep;

    time: number;

}

interface ReadCommand {

    commandType: CommandType.Read;

    book: string

}

type Command = RunCommand | SleepCommand | EatCommand;

```

Tye type `Command` is a message in my .proto like:

```proto3

syntax = "proto3"

enum CommandType {

    RUN = 0;

    SLEEP = 1;

    READ = 2;

}

message Command {

    CommandType commandType = 0;

    ...

}

```

How can I set the rest properties of the message `Command`?

[Gary Peck]

One way to model this in protobuf is using `oneof`, in which case you don't even really need the enum:

```proto

syntax = "proto3"

message RunCommand {

    string destination = 1;

}

message SleepCommand {

    int32 time = 1;

}

message ReadCommand {

    string book = 1;

}

message Command {

    oneof command_type {

        RunCommand run = 1;

        SleepCommand sleep = 2;

        ReadCommand read = 3;

    }

}

```

Gary