The State Value

Before we can continue to talk about the different layers, we have to talk about the StateValue.

As mentioned, the StateValue is how the different layers talk to each other. If the Agent, Connection and State cannot assume anything about one another, how can they share the data between them?

The StateValue is a trait that requires a single function to serialize the data into a byte vector. It is up to the state layer to determine how the data should be treated. The agent and connection layers are merely responsible for transferring the data as-is from the consumer to the state.

#![allow(unused)]
fn main() {
pub trait StateValue: Send + Sync {
    fn as_bytes(&self) -> Option<Vec<u8>>;
}
}

As you can see, the implementer of a StateValue must implement the as_bytes function that serializes the value into a u8 vector.

Here's how the Default state layer implements the StateValue trait:

#![allow(unused)]
fn main() {
impl StateValue for Value {
    fn as_bytes(&self) -> Option<Vec<u8>> {
        serde_json::to_vec(self).ok()
    }
}
}

As you will learn when we walk through the Default state layer implementation, the Value is a struct that holds a single value in the state. The value is JSON compatible so the Default state uses the serde_json crate to serialize the value into a u8 vector.

When deserializing a u8 vector into a Value struct, the Default state layer assumes the u8 vector represents a valid JSON data. It's up to the user to make sure they conform to the state requirements.