Create a Command Handler

To create a command, we need a Command Handler class to do the command processing. In the Quickstart tutorial, we used the tinker command handler. Now we’re going to create one of our own.

Our goals system has two commands. Let’s tackle the set goals command first.

`goals/set <goals>` - Sets goals.

Create the Set Goals Command

Create a file named set_goals_cmd.rb in aresmush/plugins/custom. Give it the following contents:

module AresMUSH
  module Custom
    class SetGoalsCmd
      include CommandHandler
      attr_accessor :goals

      def parse_args
       self.goals = trim_arg(cmd.args)

      def handle
        enactor.update(goals: self.goals)
        client.emit_success "Goals set!"

Then modify the get_cmd_handler method in aresmush/plugins/custom/custom.rb to wire up the command handler:

def self.get_cmd_handler(client, cmd, enactor)
  case cmd.root
  when "goals"
    case cmd.switch
    when "set"
      return SetGoalsCmd
  return nil

In the game, type load custom to reload the custom plugin.

Type goals/set Some goals. to set some goals on yourself.

Type ruby enactor.goals to view them.

About Command Handlers

When we were tinkering in the Quickstart tutorial, we just smushed all of our command processing into the handle method. But for real commands, that can get unwieldy. There’s a better way to do it.

Just as the CommandHandler utility gives us some useful utilities like enactor and client, it also gives us a structured way to handle commands. There are three steps:

  • Parse the command arguments.
  • Perform error checking and abort if there are any problems.
  • Execute the command.

Splitting up the code into multiple methods makes it more organized and readable.

In this example, the parse_args method takes the arguments from cmd.args and stuffs it into a class variable named goals. The trim_arg processing strips off any leading or trailing spaces.

The handle method takes the goals (again from self.goals) and updates the goals database attribute on the enactor. It then emits a success message to the client.

Goals are just a free-form string, so there isn’t any error checking to do here.

About the Command Dispatcher

We’ve talked a lot about how commands get handled, but how do you get from the player typing “goals/set” in their MU client to the SetGoalsCmd class? The answer is the Dispatcher.

One of the Dispatcher’s jobs is calling each plugin’s get_cmd_handler method any time it gets a command. A plugin can return nil - if they don’t want the command - or an appropriate command handler if they do.

In this example, we have a simple case statement that returns the SetGoalsCmd class if the command root is ‘goals’ and the switch is ‘set’.

You can learn more about the dispatcher in the Advanced Tutorial on Command Dispatching.

This article is part of the Adding a Command tutorial.