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60 lines
1.8 KiB
Markdown
60 lines
1.8 KiB
Markdown
# 钩子函数
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[`钩子编程`](https://zh.wikipedia.org/wiki/%E9%92%A9%E5%AD%90%E7%BC%96%E7%A8%8B)
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> 钩子编程（hooking），也称作“挂钩”，是计算机程序设计术语，指通过拦截软件模块间的函数调用、消息传递、事件传递来修改或扩展操作系统、应用程序或其他软件组件的行为的各种技术。处理被拦截的函数调用、事件、消息的代码，被称为钩子（hook）。
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在 `nonebot2` 中有一系列预定义的钩子函数，这些函数位于 [`nonebot.message`](https://v2.nonebot.dev/api/message.html) 模块下，我们可以以装饰器的形式利用这些函数，进行以下四种操作：
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:::warning 注意
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1.在钩子函数中，与 `matcher` 运行状态相关的函数将不可用，如 `matcher.finish()`
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2.如果需要在钩子函数中打断整个对话的执行，请参考以下范例：
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```python
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from nonebot.exception import IgnoredException
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@event_preprocessor
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async def do_something(bot: Bot, event: Event, state: T_State):
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raise IgnoredException("reason")
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```
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:::
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## 事件预处理
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```python
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from nonebot.message import event_preprocessor
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@event_preprocessor
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async def do_something(bot: Bot, event: Event, state: T_State):
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pass
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```
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## 事件后处理
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```python
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from nonebot.message import event_postprocessor
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@event_postprocessor
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async def do_something(bot: Bot, event: Event, state: T_State):
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pass
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```
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## 运行预处理
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```python
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from nonebot.message import run_preprocessor
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@run_preprocessor
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async def do_something(matcher: Matcher, bot: Bot, event: Event, state: T_State):
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pass
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```
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## 运行后处理
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```python
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from nonebot.message import run_postprocessor
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@run_postprocessor
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async def do_something(matcher: Matcher, exception: Optional[Exception], bot: Bot, event: Event, state: T_State):
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pass
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``` |