Discord.py中App Command无法接收List类型参数报错问题求助

嗨，我之前也遇到过一模一样的问题，这就来帮你解决！

首先先看你贴出来的代码和报错信息：

你的原代码片段：

@client.tree.command()
@app_commands.describe(members='The members you want to get the joined date from; defaults to the user who uses the command')
async def joined(interaction: discord.Interaction, members: Optional[List[discord.Member]]):
    """Says when a members joined."""
    # If no member is explicitly provided then we use the command user here
    members = members or [interaction.user]
    text = ""
    for member in members:
        text += f'{member} joined {discord.utils.format_dt(member.joined_at)}\n'
    # The format_dt function formats the date time into a human readable representation in the official client
    await interaction.response.send_message(text)

你尝试使用的命令：

/joined Member1 Member2 Member3 ...

遇到的错误：

unsupported type annotation typing.List[discord.member.Member]
File "*", line *, in
async def joined(interaction: discord.Interaction, me...

问题原因 #

Discord.py的app_commands系统并不支持直接用List[X]作为参数注解来实现多选功能，它有专门的类型来处理这种需要接收多个同类型参数的场景——那就是app_commands.Greedy。

解决方案 #

只需要把参数的类型注解从Optional[List[discord.Member]]改成Optional[app_commands.Greedy[discord.Member]]就可以了，同时要确保你已经导入了Greedy类型。

修改后的代码如下：

# 先确保导入了Greedy
from discord import app_commands

@client.tree.command()
@app_commands.describe(members='The members you want to get the joined date from; defaults to the user who uses the command')
async def joined(interaction: discord.Interaction, members: Optional[app_commands.Greedy[discord.Member]]):
    """Says when a members joined."""
    # If no member is explicitly provided then we use the command user here
    members = members or [interaction.user]
    text = ""
    for member in members:
        text += f'{member} joined {discord.utils.format_dt(member.joined_at)}\n'
    # The format_dt function formats the date time into a human readable representation in the official client
    await interaction.response.send_message(text)

补充说明 #

Greedy类型的作用就是自动收集所有传入的同类型参数，当没有传入任何成员时，members会是None，这时候你的members = members or [interaction.user]逻辑依然能正常工作，完美兼容原来的需求。现在你再用/joined Member1 Member2 Member3这样的命令就不会报错啦！

备注：内容来源于stack exchange，提问作者Vanyla Self