cqrs-es2 0.8.0

A Rust library providing lightweight CQRS and event sourcing framework.
Documentation 
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use serde::{
    de::DeserializeOwned,
    Serialize,
};
use std::fmt::Debug;

use crate::{
    commands::ICommand,
    events::{
        IEvent,
        IEventConsumer,
    },
};

/// A `Query` is a read element in a CQRS system. As events are
/// emitted multiple downstream queries are updated to reflect the
/// current state of the system. A query may also be referred to as a
/// 'view', the concepts are identical but 'query' is used here to
/// conform with CQRS nomenclature.
///
/// Queries are generally serialized for persistence, usually in a
/// standard database, but a query could also utilize messaging
/// platform or other asynchronous, eventually-consistent systems.
/// # Examples
/// ```rust
/// use serde::{
///     Deserialize,
///     Serialize,
/// };
/// use std::fmt::Debug;
///
/// use cqrs_es2::{
///     example_impl::{
///         Customer,
///         CustomerEvent,CustomerCommand
///     },
///     EventContext,
///     IEventConsumer,
///     IQuery,
/// };
///
/// #[derive(
///     Debug,
///     PartialEq,
///     Default,
///     Clone,
///     Serialize,
///     Deserialize
/// )]
/// pub struct CustomerContactQuery {
///     pub name: String,
///     pub email: String,
///     pub latest_address: String,
/// }
///
/// impl IQuery<CustomerCommand, CustomerEvent> for CustomerContactQuery {
///     fn query_type() -> &'static str {
///         "customer_contact_query"
///     }
/// }
///
/// impl IEventConsumer<CustomerCommand, CustomerEvent> for CustomerContactQuery {
///     fn update(
///         &mut self,
///         event: &EventContext<CustomerCommand, CustomerEvent>,
///     ) {
///         match &event.payload {
///             CustomerEvent::NameAdded(payload) => {
///                 self.name = payload.changed_name.clone();
///             },
///             CustomerEvent::EmailUpdated(payload) => {
///                 self.email = payload.new_email.clone();
///             },
///             CustomerEvent::AddressUpdated(payload) => {
///                 self.latest_address = payload.new_address.clone();
///             },
///         }
///     }
/// }
/// ```
pub trait IQuery<C: ICommand, E: IEvent>:
    Debug
    + PartialEq
    + Default
    + Clone
    + Serialize
    + DeserializeOwned
    + IEventConsumer<C, E>
    + Sync
    + Send {
    /// query_type is a unique identifier for this query
    fn query_type() -> &'static str;
}