Trait cqrs_es2::IQuery[−][src]

pub trait IQuery<C: ICommand, E: IEvent>: Debug + PartialEq + Default + Clone + Serialize + DeserializeOwned + IEventConsumer<C, E> + Sync + Send {
    fn query_type() -> &'static str;
}

Expand description

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

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();
            },
        }
    }
}

Trait cqrs_es2::IQuery[−][src]

Examples

Required methods

fn query_type() -> &'static str

Implementors