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use std::collections::HashMap;
/**
* Impl this trait to create a link between an entity and a structure.
*/
pub trait Model {
type Entity: crate::Entity;
type Structure: crate::Structure;
fn new(connection: &crate::Connection) -> Self;
/**
* This method creates a projection based on the structure definition of
* the underlying relation.
*
* This method can be used where a projection that sticks to table
* definition is needed like recursive CTEs. For normal projections, use
* [`create_projection`] instead.
*
* [`create_projection`]: #method.create_projection
*/
#[must_use]
fn default_projection() -> crate::Projection {
use crate::Projectable;
crate::Projection::new(Self::Structure::relation(), Self::Structure::columns())
}
/**
* This is a helper to create a new projection according to the current
* structure. Overriding this method will change projection for all models.
*/
#[must_use]
fn create_projection() -> crate::Projection {
Self::default_projection()
}
/**
* Create a new entity.
*/
#[must_use]
fn create_entity(tuple: &crate::Tuple<'_>) -> Self::Entity {
<Self::Entity as crate::Entity>::from(tuple)
}
fn primary_key(
entity: &Self::Entity,
) -> crate::Result<HashMap<&'static str, &dyn crate::ToSql>> {
use crate::Entity;
use crate::Structure;
let mut pk = HashMap::new();
for field in Self::Structure::primary_key() {
pk.insert(*field, entity.get(field).ok_or(crate::Error::PrimaryKey)?);
}
if pk.is_empty() {
return Err(crate::Error::PrimaryKey);
}
Ok(pk)
}
}