# RefStruct.keys

Get the keys of the current state of a RefStruct.

## Signatures

```ts
export declare const keys: <S extends object, E, R>(ref: RefStruct<S, E, R>) => RefSubject.Computed<Array<keyof S & string>, E, R>;
```

## Why

Projects struct state with keys for both current reads and future pushes, avoiding a second
mutable cache of the derived value.

## Ownership and lifetime

The keys view retains no independent state. An Effect read samples the source once; Fx
observation follows later pushes and its observing Scope owns subscription cleanup.