tablo_core/resource/
relation.rs

1//! Relation tables: a record page's related rows through the related resource's own list table.
2
3use std::{any::TypeId, sync::Arc};
4
5use toasty::stmt::{Expr, IntoExpr, Path};
6
7use super::Resource;
8use crate::{form::FormScalar, schema::lens_field, toasty_compat::pk};
9
10/// One relation of a parent resource's records.
11///
12/// Declared by [`ResourceDef::relation`](super::ResourceDef::relation); the related resource
13/// must be registered on the same panel, which keys the relation by its slug:
14///
15/// ```text
16/// ResourceDef::new().relation(Relation::has_many::<CommentResource>(Comment::fields().post_id()))
17/// ```
18pub struct Relation<P> {
19    pub(crate) child: TypeId,
20    pub(crate) child_name: &'static str,
21    pub(crate) label: Option<String>,
22    pub(crate) foreign_key: String,
23    bind: BindFn<P>,
24    /// Why `foreign_key` binds no column, when it does not.
25    pub(crate) misdeclared: Option<crate::DeclarationErrorKind>,
26}
27
28/// An owner's rows filter on the child.
29type BindFn<P> = Arc<dyn Fn(&P) -> (Expr<bool>, String) + Send + Sync>;
30
31/// A foreign-key column type referencing a primary key of type `K`: `K` itself, or `Option<K>`
32/// for an optional reference. Sealed: these are the only two.
33pub trait ForeignKey<K>:
34    sealed::Sealed<K> + IntoExpr<Self> + FormScalar + Send + Sync + 'static
35{
36}
37
38impl<K> ForeignKey<K> for K where K: IntoExpr<K> + FormScalar + Send + Sync + 'static {}
39
40impl<K> ForeignKey<K> for Option<K> where
41    Option<K>: IntoExpr<Self> + FormScalar + Send + Sync + 'static
42{
43}
44
45mod sealed {
46    pub trait Sealed<K> {}
47
48    impl<K> Sealed<K> for K {}
49
50    impl<K> Sealed<K> for Option<K> {}
51}
52
53impl<P> Relation<P>
54where
55    P: toasty::schema::Model + IntoExpr<P> + 'static,
56{
57    /// Declare a `has_many` child resource whose `foreign_key` holds the owner's primary key, a
58    /// single column.
59    ///
60    /// ```text
61    /// Relation::has_many::<CommentResource>(Comment::fields().post_id())
62    /// ```
63    pub fn has_many<C>(foreign_key: Path<C::Model, impl ForeignKey<P::PrimaryKey>>) -> Self
64    where
65        C: Resource,
66    {
67        Self::bound_by::<C, _>(foreign_key)
68    }
69
70    fn bound_by<C, T>(foreign_key: Path<C::Model, T>) -> Self
71    where
72        C: Resource,
73        T: ForeignKey<P::PrimaryKey>,
74    {
75        // A foreign key is one column of the child: it binds against the child's model alone.
76        let (column, misdeclared) = match lens_field(
77            foreign_key.clone(),
78            &<C::Model as toasty::schema::Model>::schema(),
79        ) {
80            Ok(field) => (field.name.app_unwrap().to_string(), None),
81            Err(error) => (String::new(), Some(error)),
82        };
83        Self {
84            child: TypeId::of::<C>(),
85            child_name: std::any::type_name::<C>(),
86            label: None,
87            foreign_key: column,
88            misdeclared,
89            bind: Arc::new(move |owner| {
90                let scope = foreign_key.clone().eq(pk::pk_expr::<P, T>(owner));
91                (scope, pk::pk_text(owner))
92            }),
93        }
94    }
95}
96
97impl<P> Relation<P> {
98    /// Titles the section `label` instead of the related resource's plural label.
99    #[must_use]
100    pub fn label(mut self, label: impl Into<String>) -> Self {
101        self.label = Some(label.into());
102        self
103    }
104
105    /// The child's rows that belong to `owner`, and the owner's primary key as text.
106    pub(crate) fn bind(&self, owner: &P) -> (Expr<bool>, String) {
107        (self.bind)(owner)
108    }
109}
110
111impl<P> std::fmt::Debug for Relation<P> {
112    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
113        f.debug_struct("Relation")
114            .field("child", &self.child_name)
115            .field("label", &self.label)
116            .field("foreign_key", &self.foreign_key)
117            .finish_non_exhaustive()
118    }
119}
tablo_core/resource/relation.rs

tablo_core/resource/
relation.rs
