Observable

Mixin: notifies when fields change; auto-wraps lists/dicts to be observable.

Example: ```python import flet as ft from dataclasses import dataclass

@ft.observable
@dataclass
class MyDataClass:
    x: int
    y: int

obj = MyDataClass(1, 2)

def listener(sender, field):
    print(f"Changed: {field} in {sender}")

obj.subscribe(listener)
obj.x = 3
obj.y = 4
```

方法

名称	类型	默认值	说明
subscribe	Callable[[], None]	—	Register a change listener. Args: fn: Listener callback receiving (sender, field). Returns: A disposer function that unsubscribes the listener.
notify	—	—	Manually notify listeners that something changed.