Function fieldLens

fieldLens<
    S extends Cell<any>,
    K extends string | number | symbol,
    C extends new (...args: never[]) => Cell<Inner<S>[K]>,
>(
    parent: S,
    key: K,
    Cls: C,
): S extends WritableBrand ? Writable<InstanceType<C>> : InstanceType<C>
Bidirectional field lens onto parent.value[key] (write spread-replaces), cached per (instance, key). Writable<Cls> on a writable parent, bare Cls on RO.
```
 get x() { return fieldLens(this, "x", Num); }
```
Type Parameters
- S extends Cell<any>
- K extends string | number | symbol
- C extends new (...args: never[]) => Cell<Inner<S>[K]>
Parameters
- parent: S
- key: K
- Cls: C
Returns S extends WritableBrand ? Writable<InstanceType<C>> : InstanceType<C>
- Defined in src/core/cell.ts:2140