working on constraint design

cookbook/src/lib.rs

@@ -57,6 +57,7 @@ pub mod ingredients {
     use super::{SqliteConnection, schema};
     use super::diesel::prelude::*;
 
+    /// A wrapper of [`IngredientList`] with DB connection capacity.
     pub struct IngredientListManager<'a>(&'a SqliteConnection, IngredientList);
 
     impl<'a> IngredientListManager<'a> {
@@ -98,12 +99,9 @@ pub mod ingredients {
     fn find(conn: &SqliteConnection, name: &str) -> Option<Ingredient> {
         use self::schema::ingredients::dsl::*;
 
-        match ingredients.filter(alias.like(name))
-            .first(conn)
-        {
-            Ok(ingdt) => Some(ingdt),
-            Err(_) => None,
-        }
+        ingredients.filter(alias.like(name))
+                   .first(conn)
+                   .ok()
     }
 
     fn create(conn: &SqliteConnection, name: &str) -> Result<i32,String> {