Find related

src/entity/base.rs

@@ -49,7 +49,7 @@ pub trait EntityTrait: Iden + Default + Debug + 'static {
     /// );
     /// ```
     fn find() -> Select<Self> {
-        Select::new(Self::default())
+        Select::<Self>::new()
     }
 
     /// ```

src/entity/relation.rs

@@ -1,4 +1,4 @@
-use super::{Identity, IntoIdentity};
+use crate::{EntityTrait, Identity, IntoIdentity, Select};
 use sea_query::{Iden, IntoIden};
 use std::fmt::Debug;
 use std::rc::Rc;
@@ -14,6 +14,17 @@ pub trait RelationTrait: Debug + 'static {
     fn rel_def(&self) -> RelationDef;
 }
 
+pub trait Related<R>
+where
+    R: EntityTrait,
+{
+    fn via() -> RelationDef;
+
+    fn find_related() -> Select<R> {
+        Select::<R>::new().prepare_reverse_join(Self::via())
+    }
+}
+
 pub struct RelationDef {
     pub rel_type: RelationType,
     pub from_tbl: Rc<dyn Iden>,

src/query/select.rs

@@ -18,7 +18,7 @@ impl<E: 'static> Select<E>
 where
     E: EntityTrait,
 {
-    pub(crate) fn new(_: E) -> Self {
+    pub(crate) fn new() -> Self {
         Self {
             query: SelectStatement::new(),
             entity: PhantomData,
@@ -56,11 +56,7 @@ where
         self
     }
 
-    pub fn reverse_join<R>(mut self, rel: R) -> Self
-    where
-        R: RelationTrait,
-    {
-        let rel = rel.rel_def();
+    pub(crate) fn prepare_reverse_join(mut self, rel: RelationDef) -> Self {
         let from_tbl = rel.from_tbl.clone();
         let to_tbl = rel.to_tbl.clone();
         let owner_keys = rel.from_col;
@@ -135,6 +131,13 @@ where
         self.prepare_join(JoinType::InnerJoin, E::Relation::rel_def(&rel))
     }
 
+    pub fn reverse_join<R>(self, rel: R) -> Self
+    where
+        R: RelationTrait,
+    {
+        self.prepare_reverse_join(rel.rel_def())
+    }
+
     /// Get a mutable ref to the query builder
     pub fn query(&mut self) -> &mut SelectStatement {
         &mut self.query
@@ -211,4 +214,20 @@ mod tests {
             .join(" ")
         );
     }
+
+    #[test]
+    fn join_4() {
+        assert_eq!(
+            cake::Entity::find_fruit()
+                .filter(cake::Column::Id.eq(11))
+                .build(MysqlQueryBuilder)
+                .to_string(),
+            [
+                "SELECT `fruit`.`id`, `fruit`.`name`, `fruit`.`cake_id` FROM `fruit`",
+                "INNER JOIN `cake` ON `cake`.`id` = `fruit`.`cake_id`",
+                "WHERE `cake`.`id` = 11",
+            ]
+            .join(" ")
+        );
+    }
 }

src/tests_cfg/cake.rs

@@ -1,6 +1,6 @@
 use crate::{
     ColumnTrait, ColumnType, EntityTrait, EnumIter, Iden, Identity, IntoIdentity, ModelTrait,
-    QueryResult, RelationDef, RelationTrait, TypeErr,
+    QueryResult, Related, RelationDef, RelationTrait, Select, TypeErr,
 };
 
 #[derive(Default, Debug, Iden)]
@@ -66,3 +66,15 @@ impl RelationTrait for Relation {
         }
     }
 }
+
+impl Related<super::fruit::Entity> for Entity {
+    fn via() -> RelationDef {
+        Relation::Fruit.rel_def()
+    }
+}
+
+impl Entity {
+    pub fn find_fruit() -> Select<super::fruit::Entity> {
+        Self::find_related()
+    }
+}