has_many_key

📍 Method

has_many_key<T: Entity>(&self, entity: &T) -> Self::ID

Extracts the foreign key value from the entity that references the current entity as its parent. This method is used in conjunction with the #[has_many] attribute to identify which field in the child entity structure and field type serves as the foreign key linking it to the parent entity. This allows you to easily access the parent entity’s ID when working with entities without needing to know the specific field name of the foreign key.

🧩 Detailed Example:

use repox::Entity;

#[derive(Debug, Clone, PartialEq, Entity)]
#[has_many(WidgetProvision.widget_id)]
pub struct Widget {
    pub id: u32,
    pub name: String,
}

#[derive(Debug, Clone, PartialEq, Entity)]
pub struct WidgetProvision {
    pub id: u128,
    pub widget_id: u32,
    pub float: f64,
}

let foo = Widget { id: 1, name: "foo".into() };
let provision = WidgetProvision { id: 2, widget_id: 42, float: 1.337 };

assert_eq!(foo.has_many_key::<WidgetProvision>(&provision), 42);