Add converter example

examples/converters.py

@@ -0,0 +1,113 @@
+# This example requires the 'members' privileged intent to use the Member converter.
+
+import typing
+
+import discord
+from discord.ext import commands
+
+intents = discord.Intents.default()
+intents.members = True
+
+bot = commands.Bot('!', intents=intents)
+
+
+@bot.command()
+async def userinfo(ctx: commands.Context, user: discord.User):
+    # In the command signature above, you can see that the `user`
+    # parameter is typehinted to `discord.User`. This means that
+    # during command invocation we will attempt to convert
+    # the value passed as `user` to a `discord.User` instance.
+    # The documentation notes what can be converted, in the case of `discord.User`
+    # you pass an ID, mention or username (discrim optional)
+    # E.g. 80088516616269824, @Danny or Danny#0007
+
+    # NOTE: typehinting acts as a converter within the `commands` framework only.
+    # In standard Python, it is use for documentation and IDE assistance purposes.
+
+    # If the conversion is successful, we will have a `discord.User` instance
+    # and can do the following:
+    user_id = user.id
+    username = user.name
+    avatar = user.avatar_url
+    await ctx.send('User found: {} -- {}\n{}'.format(user_id, username, avatar))
+
+@userinfo.error
+async def userinfo_error(ctx: commands.Context, error: commands.CommandError):
+    # if the conversion above fails for any reason, it will raise `commands.BadArgument`
+    # so we handle this in this error handler:
+    if isinstance(error, commands.BadArgument):
+        return await ctx.send('Couldn\'t find that user.')
+
+# Custom Converter here
+class ChannelOrMemberConverter(commands.Converter):
+    async def convert(self, ctx: commands.Context, argument: str):
+        # In this example we have made a custom converter.
+        # This checks if an input is convertible to a
+        # `discord.Member` or `discord.TextChannel` instance from the
+        # input the user has given us using the pre-existing converters
+        # that the library provides.
+
+        member_converter = commands.MemberConverter()
+        try:
+            # Try and convert to a Member instance.
+            # If this fails, then an exception is raised.
+            # Otherwise, we just return the converted member value.
+            member = await member_converter.convert(ctx, argument)
+        except commands.MemberNotFound:
+            pass
+        else:
+            return member
+
+        # Do the same for TextChannel...
+        textchannel_converter = commands.TextChannelConverter()
+        try:
+            channel = await textchannel_converter.convert(ctx, argument)
+        except commands.ChannelNotFound:
+            pass
+        else:
+            return channel
+
+        # If the value could not be converted we can raise an error
+        # so our error handlers can deal with it in one place.
+        # The error has to be CommandError derived, so BadArgument works fine here.
+        raise commands.BadArgument('No Member or TextChannel could be converted from "{}"'.format(argument))
+
+
+
+@bot.command()
+async def notify(ctx: commands.Context, target: ChannelOrMemberConverter):
+    # This command signature utilises the custom converter written above
+    # What will happen during command invocation is that the `target` above will be passed to
+    # the `argument` parameter of the `ChannelOrMemberConverter.convert` method and 
+    # the conversion will go through the process defined there.
+
+    await target.send('Hello, {}!'.format(target.name))
+
+@bot.command()
+async def ignore(ctx: commands.Context, target: typing.Union[discord.Member, discord.TextChannel]):
+    # This command signature utilises the `typing.Union` typehint.
+    # The `commands` framework attempts a conversion of each type in this Union *in order*.
+    # So, it will attempt to convert whatever is passed to `target` to a `discord.Member` instance.
+    # If that fails, it will attempt to convert it to a `discord.TextChannel` instance.
+    # See: https://discordpy.readthedocs.io/en/latest/ext/commands/commands.html#typing-union
+    # NOTE: If a Union typehint converter fails it will raise `commands.BadUnionArgument`
+    # instead of `commands.BadArgument`.
+
+    # To check the resulting type, `isinstance` is used
+    if isinstance(target, discord.Member):
+        await ctx.send('Member found: {}, adding them to the ignore list.'.format(target.mention))
+    elif isinstance(target, discord.TextChannel): # this could be an `else` but for completeness' sake.
+        await ctx.send('Channel found: {}, adding it to the ignore list.'.format(target.mention))
+
+# Built-in type converters.
+@bot.command()
+async def multiply(ctx: commands.Context, number: int, maybe: bool):
+    # We want an `int` and a `bool` parameter here.
+    # `bool` is a slightly special case, as shown here:
+    # See: https://discordpy.readthedocs.io/en/latest/ext/commands/commands.html#bool
+
+    if maybe is True:
+        return await ctx.send(number * 2)
+    await ctx.send(number * 5)
+
+bot.run('token')