Hands-On Microservices with Rust

Using database actors

In the previous example in this chapter, we used shared State to provide access to a counter stored as i64, wrapped with RefCell. We reuse this struct, but add a CacheLink field to use connections with a CacheActor to get or set cached values. Add this field:

struct State {    counter: RefCell<i64>,    cache: CacheLink,}

We derived a Default trait for the State struct before, but now we need a new constructor, because we have to provide a CacheLink instance with the actual address of the caching actor:

impl State {    fn new(cache: CacheLink) -> Self {        Self {            counter: RefCell::default(),            cache,        }    }}

In most cases, caching works this way—it tries to extract a value from a cache; if it exists and hasn't expired, then the value ...