Function refresh

refresh<T extends Resource>(): OperatorFunction<
    T
    | null
    | undefined,
    T | undefined,
>
Returns an RxJS operator to refresh a Resource or Collection of resources. It is equivalent to
```
switchMap(resource => of(undefined))
```
if resource is null or undefined and to
```
switchMap(resource => resource.read())
```
otherwise.
Type Parameters
- T extends Resource
Returns OperatorFunction<T | null | undefined, T | undefined>
a function that transforms the source Observable
- Defined in rxjs.ts:121