# RefStruct.pick

Pick properties from the current state of a RefStruct.

## Signatures

```ts
export declare const pick: {
    <S extends object, const Keys extends ReadonlyArray<keyof S>>(keys: Keys): <E, R>(ref: RefStruct<S, E, R>) => RefSubject.Computed<Pick<S, Keys[number]>, E, R>;
    <S extends object, const Keys extends ReadonlyArray<keyof S>, E, R>(ref: RefStruct<S, E, R>, keys: Keys): RefSubject.Computed<Pick<S, Keys[number]>, E, R>;
};
```

## Why

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

## Ownership and lifetime

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