cast_core/
relation.rs

1//! Relationship definitions. `RelationDef` is implemented by zero-sized types
2//! generated by `#[has_many]` / `#[belongs_to]` attribute parsing.
3
4use std::marker::PhantomData;
5
6use crate::model::Model;
7use crate::Error;
8
9pub trait RelationKind: Send + Sync + 'static {}
10
11pub struct HasMany;
12impl RelationKind for HasMany {}
13
14pub struct HasOne;
15impl RelationKind for HasOne {}
16
17pub struct BelongsTo;
18impl RelationKind for BelongsTo {}
19
20pub struct BelongsToMany;
21impl RelationKind for BelongsToMany {}
22
23pub trait RelationDef: Send + Sync {
24    type Parent: Model;
25    type Child: Model;
26    type Kind: RelationKind;
27    fn local_key() -> &'static str;
28    fn foreign_key() -> &'static str;
29}
30
31/// A live relation handle: from a parent row, load the related rows.
32pub struct Relation<P: Model, C: Model, K: RelationKind> {
33    pub parent_value: serde_json::Value,
34    pub local_key: &'static str,
35    pub foreign_key: &'static str,
36    _marker: PhantomData<(P, C, K)>,
37}
38
39impl<P: Model, C: Model> Relation<P, C, HasMany> {
40    pub async fn load(self, pool: &sqlx::PgPool) -> Result<Vec<C>, Error> {
41        let sql = format!(
42            "SELECT {} FROM {} WHERE {} = $1",
43            C::COLUMNS.join(", "),
44            C::TABLE,
45            self.foreign_key,
46        );
47        let rows = sqlx::query_as::<_, C>(&sql)
48            .bind(self.parent_value)
49            .fetch_all(pool)
50            .await?;
51        Ok(rows)
52    }
53}
54
55impl<P: Model, C: Model> Relation<P, C, BelongsTo> {
56    pub async fn load(self, pool: &sqlx::PgPool) -> Result<Option<C>, Error> {
57        let sql = format!(
58            "SELECT {} FROM {} WHERE {} = $1 LIMIT 1",
59            C::COLUMNS.join(", "),
60            C::TABLE,
61            self.local_key,
62        );
63        let row = sqlx::query_as::<_, C>(&sql)
64            .bind(self.parent_value)
65            .fetch_optional(pool)
66            .await?;
67        Ok(row)
68    }
69}
70
71impl<P: Model, C: Model> Relation<P, C, HasOne> {
72    pub async fn load(self, pool: &sqlx::PgPool) -> Result<Option<C>, Error> {
73        let sql = format!(
74            "SELECT {} FROM {} WHERE {} = $1 LIMIT 1",
75            C::COLUMNS.join(", "),
76            C::TABLE,
77            self.foreign_key,
78        );
79        let row = sqlx::query_as::<_, C>(&sql)
80            .bind(self.parent_value)
81            .fetch_optional(pool)
82            .await?;
83        Ok(row)
84    }
85}
86
87impl<P: Model, C: Model, K: RelationKind> Relation<P, C, K> {
88    pub fn new(
89        parent_value: serde_json::Value,
90        local_key: &'static str,
91        foreign_key: &'static str,
92    ) -> Self {
93        Self {
94            parent_value,
95            local_key,
96            foreign_key,
97            _marker: PhantomData,
98        }
99    }
100}
cast_core/relation.rs

cast_core/
relation.rs
