nonebot2/archive/2.0.0a11/advanced/runtime-hook.md
2021-03-23 23:10:05 +08:00

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# 钩子函数
[`钩子编程`](https://zh.wikipedia.org/wiki/%E9%92%A9%E5%AD%90%E7%BC%96%E7%A8%8B)
> 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
`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:
:::warning 注意
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()`
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:
```python
from nonebot.exception import IgnoredException
@event_preprocessor
async def do_something(bot: Bot, event: Event, state: T_State):
raise IgnoredException("reason")
```
:::
## 事件预处理
```python
from nonebot.message import event_preprocessor
@event_preprocessor
async def do_something(bot: Bot, event: Event, state: T_State):
pass
```
## 事件后处理
```python
from nonebot.message import event_postprocessor
@event_postprocessor
async def do_something(bot: Bot, event: Event, state: T_State):
pass
```
## 运行预处理
```python
from nonebot.message import run_preprocessor
@run_preprocessor
async def do_something(matcher: Matcher, bot: Bot, event: Event, state: T_State):
pass
```
## 运行后处理
```python
from nonebot.message import run_postprocessor
@run_postprocessor
async def do_something(matcher: Matcher, exception: Optional[Exception], bot: Bot, event: Event, state: T_State):
pass
```