Located Values

As we have seen in the Choreography section, a located value is a value that is available only at a specific location. In this section, we will discuss located values in more detail.

Located struct

The Located struct represents a located value. It is a generic struct that takes two type parameters: a type parameter V that represents the type of the value, and a type parameter L1 that represents the location where the value is available.

pub struct Located<V, L1>
    L1: ChoreographyLocation,
    // ...

The Located struct can be in one of the two states: Local and Remote. The Local state represents a located value that is available at the current location. The Remote state represents a located value that is available at a different location.

Portable trait

Located values can be sent from one location to another using the comm operator and unwrapped using the broadcast operator if the value type implements the Portable trait.

trait Portable: Serialize + DeserializeOwned {}

The Portable is defined as above. The Serialize and DeserializeOwned traits are from the serde crate and are used to serialize and deserialize the value for communication.

The chorus_lib crate re-exports the Serialize and Deserialize from serde. In many cases, those traits can automatically be derived using the #[derive(Serialize, Deserialize)] attribute.

For the complete list of types that supports automatic derivation of Serialize and Deserialize, see the serde documentation. The documentation also explains how to implement Serialize and Deserialize for custom types.