Introduce a find_by! macro to avoid some code duplication

src/models/comments.rs

@@ -62,19 +62,8 @@ impl Comment {
             .into_iter().nth(0)
     }
 
-    pub fn find_by_post(conn: &PgConnection, post_id: i32) -> Vec<Comment> {
-        comments::table.filter(comments::post_id.eq(post_id))
-            .load::<Comment>(conn)
-            .expect("Error loading comment by post id")
-    }
-
-    pub fn find_by_ap_url(conn: &PgConnection, ap_url: String) -> Option<Comment> {
-        comments::table.filter(comments::ap_url.eq(ap_url))
-            .limit(1)
-            .load::<Comment>(conn)
-            .expect("Error loading comment by AP URL")
-            .into_iter().nth(0)
-    }
+    find_by!(comments, find_by_post, post_id as i32);
+    find_by!(comments, find_by_ap_url, ap_url as String);
 
     pub fn get_author(&self, conn: &PgConnection) -> User {
         User::get(conn, self.author_id).unwrap()

src/models/instance.rs

@@ -63,13 +63,7 @@ impl Instance {
             .into_iter().nth(0)
     }
 
-    pub fn find_by_domain(conn: &PgConnection, domain: String) -> Option<Instance> {
-        instances::table.filter(instances::public_domain.eq(domain))
-            .limit(1)
-            .load::<Instance>(conn)
-            .expect("Couldn't load instance by domain")
-            .into_iter().nth(0)
-    }
+    find_by!(instances, find_by_domain, public_domain as String);
 
     pub fn block(&self) {
         unimplemented!()

src/models/likes.rs

@@ -58,13 +58,7 @@ impl Like {
             .into_iter().nth(0)
     }
 
-    pub fn find_by_ap_url(conn: &PgConnection, ap_url: String) -> Option<Like> {
-        likes::table.filter(likes::ap_url.eq(ap_url))
-            .limit(1)
-            .load::<Like>(conn)
-            .expect("Error loading like by AP URL")
-            .into_iter().nth(0)
-    }
+    find_by!(likes, find_by_ap_url, ap_url as String);
 
     pub fn find_by_user_on_post(conn: &PgConnection, user: &User, post: &Post) -> Option<Like> {
         likes::table.filter(likes::post_id.eq(post.id))

src/models/mod.rs

@@ -1,3 +1,17 @@
+// TODO: support multiple columns (see Like::find_by_user_on_post)
+macro_rules! find_by {
+    ($table:ident, $fn:ident, $col:ident as $type:ident) => {
+        /// Try to find a $table with a given $col
+        pub fn $fn(conn: &PgConnection, val: $type) -> Option<Self> {
+            $table::table.filter($table::$col.eq(val))
+                .limit(1)
+                .load::<Self>(conn)
+                .expect("Error loading $table by $col")
+                .into_iter().nth(0)
+        }
+    };
+}
+
 pub mod blog_authors;
 pub mod blogs;
 pub mod comments;

src/models/posts.rs

@@ -76,21 +76,8 @@ impl Post {
             .len()
     }
 
-    pub fn find_by_slug(conn: &PgConnection, slug: String) -> Option<Post> {
-        posts::table.filter(posts::slug.eq(slug))
-            .limit(1)
-            .load::<Post>(conn)
-            .expect("Error loading post by slug")
-            .into_iter().nth(0)
-    }
-
-    pub fn find_by_ap_url(conn: &PgConnection, ap_url: String) -> Option<Post> {
-        posts::table.filter(posts::ap_url.eq(ap_url))
-            .limit(1)
-            .load::<Post>(conn)
-            .expect("Error loading post by AP URL")
-            .into_iter().nth(0)
-    }
+    find_by!(posts, find_by_slug, slug as String);
+    find_by!(posts, find_by_ap_url, ap_url as String);
 
     pub fn get_recents(conn: &PgConnection, limit: i64) -> Vec<Post> {
         posts::table.order(posts::creation_date.desc())

src/models/reshares.rs

@@ -51,13 +51,7 @@ impl Reshare {
         }
     }
 
-    pub fn find_by_ap_url(conn: &PgConnection, ap_url: String) -> Option<Reshare> {
-        reshares::table.filter(reshares::ap_url.eq(ap_url))
-            .limit(1)
-            .load::<Reshare>(conn)
-            .expect("Error loading reshare by AP URL")
-            .into_iter().nth(0)
-    }
+    find_by!(reshares, find_by_ap_url, ap_url as String);
 
     pub fn find_by_user_on_post(conn: &PgConnection, user: &User, post: &Post) -> Option<Reshare> {
         reshares::table.filter(reshares::post_id.eq(post.id))

src/models/users.rs

@@ -125,13 +125,7 @@ impl User {
             .len()
     }
 
-    pub fn find_by_email(conn: &PgConnection, email: String) -> Option<User> {
-        users::table.filter(users::email.eq(email))
-            .limit(1)
-            .load::<User>(conn)
-            .expect("Error loading user by email")
-            .into_iter().nth(0)
-    }
+    find_by!(users, find_by_email, email as String);
 
     pub fn find_by_name(conn: &PgConnection, username: String, instance_id: i32) -> Option<User> {
         users::table.filter(users::username.eq(username))