# reducers

URL: /milo-cli/api/milo/reducers/
Section: milo
Description: Composable reducer combinators for common interaction patterns.

Decorators that wrap reducers to handle boilerplate key handling —
quit on escape, cursor navigation, enter to confirm — so the inner
reducer only contains app-specific logic.

Usage::

    @quit_on("q", SpecialKey.ESCAPE)
    @with_cursor("items", wrap=True)
    @with_confirm()
    def reducer(state, action):
        # only app-specific logic here
        ...

---

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Module

#
`reducers`

Composable reducer combinators for common interaction patterns.

Decorators that wrap reducers to handle boilerplate key handling —
quit on escape, cursor navigation, enter to confirm — so the inner
reducer only contains app-specific logic.

Usage::

```
@quit_on("q", SpecialKey.ESCAPE)
@with_cursor("items", wrap=True)
@with_confirm()
def reducer(state, action):
    # only app-specific logic here
    ...
```

5Functions

## Functions

`_match_key`

2

`bool`

▼

Check if a Key matches a target (char string or SpecialKey).

`def _match_key(key: Key, target: str | SpecialKey) -> bool`

##### Parameters

Name
Type
Description

`key`
`Key`

`target`
`str | SpecialKey`

##### Returns

`bool`

`_unwrap_state`

1

`Any`

▼

Extract plain state from a ReducerResult if needed.

`def _unwrap_state(result: Any) -> Any`

##### Parameters

Name
Type
Description

`result`
`Any`

##### Returns

`Any`

`quit_on`

1

`Callable`

▼

Decorator: return Quit(state) when any of the specified keys are pressed.

Keys…

`def quit_on(*keys: str | SpecialKey) -> Callable`

Decorator: return Quit(state) when any of the specified keys are pressed.

Keys can be character strings (`"q"`) or SpecialKey enums
(`SpecialKey.ESCAPE`). The inner reducer runs first so it can
perform app-specific quit logic (e.g. setting flags); if it already
returned`Quit`, the wrapper passes it through unchanged.

Usage::

```
@quit_on("q", SpecialKey.ESCAPE)
def reducer(state, action):
    ...
```

##### Parameters

Name
Type
Description

`*keys`
`str | SpecialKey`

##### Returns

`Callable`

`with_cursor`

3

`Callable`

▼

Decorator: add up/down arrow cursor navigation over a list field.

Expects *sta…

`def with_cursor(items_field: str, cursor_field: str = 'cursor', *, wrap: bool = False) -> Callable`

Decorator: add up/down arrow cursor navigation over a list field.

Expects state to be a frozen dataclass with an attribute named
items_field (the sequence) and cursor_field (an`int`).
Handles`SpecialKey.UP` and `SpecialKey.DOWN`, clamping or
wrapping as configured.

The inner reducer runs first. If it returns`Quit`or
`ReducerResult`, the wrapper does not interfere.

Usage::

```
@with_cursor("entries", wrap=True)
def reducer(state, action):
    ...
```

##### Parameters

Name
Type
Description

`items_field`
`str`

`cursor_field`
`str`

Default:`'cursor'`

`wrap`
`bool`

Default:`False`

##### Returns

`Callable`

`with_confirm`

1

`Callable`

▼

Decorator: return Quit(state) when the confirm key is pressed.

Useful for sele…

`def with_confirm(key: str | SpecialKey = SpecialKey.ENTER) -> Callable`

Decorator: return Quit(state) when the confirm key is pressed.

Useful for selection-style apps where pressing Enter chooses the
current item. The inner reducer runs first; if it already returned
`Quit`, the wrapper does nothing.

Usage::

```
@with_confirm()
@with_cursor("items")
@quit_on("q", SpecialKey.ESCAPE)
def reducer(state, action):
    ...
```

##### Parameters

Name
Type
Description

`key`
`str | SpecialKey`

Default:`SpecialKey.ENTER`

##### Returns

`Callable`