Gears

There comes a point in your bot’s development when you want to organize a collection of commands, listeners, and some state into one class. Gears allow you to do just that.

The gist:

It should be noted that gears are typically used alongside with Extensions.

Quick Example

This example gear defines a Greetings category for your commands, with a single command named hello as well as a listener to listen to an Event.

class Greetings(commands.Gear):
    def __init__(self, bot):
        self.bot = bot
        self._last_member = None

    @commands.Gear.listener()
    async def on_member_join(self, event: stoat.ServerMemberJoinEvent):
        member = event.member
        server = member.server

        if server.system_messages is None:
            return

        channel = server.system_messages.user_joined

        if channel is None:
            return

        await member.state.http.send_message(channel, f'Welcome {member.mention}.')

    @commands.command()
    async def hello(self, ctx, *, member: typing.Optional[stoat.Member] = None):
        """Says hello"""
        member = member or ctx.author
        if self._last_member is None or self._last_member.id != member.id:
            await ctx.send(f'Hello {member.name}~')
        else:
            await ctx.send(f'Hello {member.name}... This feels familiar.')
        self._last_member = member

A couple of technical notes to take into consideration:

  • All listeners must be explicitly marked via decorator, listener().

  • The name of the gear is automatically derived from the class name but can be overridden. See Meta Options.

  • All commands must now take a self parameter to allow usage of instance attributes that can be used to maintain state.

Gear Registration

Once you have defined your gear, you need to tell the bot to register the gears to be used. We do this via the add_gear() method.

await bot.add_gear(Greetings(bot))

This binds the gear to the bot, adding all commands and listeners to the bot automatically.

Note that we reference the gear by name, which we can override through Meta Options. So if we ever want to remove the gear eventually, we would have to do the following.

await bot.remove_gear('Greetings')

Using Gears

Just as we remove a gear by its name, we can also retrieve it by its name as well. This allows us to use a gear as an inter-command communication protocol to share data. For example:

class Economy(commands.Gear):
    ...

    async def withdraw_money(self, member, money):
        # implementation here
        ...

    async def deposit_money(self, member, money):
        # implementation here
        ...

class Gambling(commands.Gear):
    def __init__(self, bot):
        self.bot = bot

    def coinflip(self):
        return random.randint(0, 1)

    @commands.command()
    async def gamble(self, ctx, money: int):
        """Gambles some money."""
        economy = self.bot.get_gear('Economy')
        if economy is not None:
            await economy.withdraw_money(ctx.author, money)
            if self.coinflip() == 1:
                await economy.deposit_money(ctx.author, money * 1.5)

Special Methods

As gears get more complicated and have more commands, there comes a point where we want to customise the behaviour of the entire gear or bot.

They are as follows:

You can visit the reference to get more detail.

Meta Options

At the heart of a gear resides a metaclass, commands.GearMeta, which can take various options to customise some of the behaviour. To do this, we pass keyword arguments to the class definition line. For example, to change the gear name we can pass the name keyword argument as follows:

class MyGear(commands.Gear, name='My Gear'):
    pass

To see more options that you can set, see the documentation of commands.GearMeta.

Inspection

Since gears ultimately are classes, we have some tools to help us inspect certain properties of the gear.

To get a list of commands, we can use Gear.get_commands().

>>> gear = bot.get_gear('Greetings')
>>> commands = gear.get_commands()
>>> print([c.name for c in commands])

If we want to get the subcommands as well, we can use the Gear.walk_commands() generator.

>>> print([c.qualified_name for c in gear.walk_commands()])

To do the same with listeners, we can query them with Gear.get_listeners(). This returns a list of tuples – the first element being the event class and the second one being the actual function itself.

>>> for cls, func in gear.get_listeners():
...     print(cls, '->', func)