IDatabase::load should return D not take a mutable reference of it (#99)

Closes #96

Reviewed-on: #99

src/database/json/mod.rs

@@ -1,11 +1,10 @@
 //! Module for storing MusicHoard data in a JSON file database.
 
-use serde::de::DeserializeOwned;
-use serde::Serialize;
-
 #[cfg(test)]
 use mockall::automock;
 
+use crate::Collection;
+
 use super::{IDatabase, LoadError, SaveError};
 
 pub mod backend;
@@ -46,13 +45,12 @@ impl<JDB: IJsonDatabaseBackend> JsonDatabase<JDB> {
 }
 
 impl<JDB: IJsonDatabaseBackend> IDatabase for JsonDatabase<JDB> {
-    fn load<D: DeserializeOwned>(&self, collection: &mut D) -> Result<(), LoadError> {
+    fn load(&self) -> Result<Collection, LoadError> {
         let serialized = self.backend.read()?;
-        *collection = serde_json::from_str(&serialized)?;
-        Ok(())
+        Ok(serde_json::from_str(&serialized)?)
     }
 
-    fn save<S: Serialize>(&mut self, collection: &S) -> Result<(), SaveError> {
+    fn save(&mut self, collection: &Collection) -> Result<(), SaveError> {
         let serialized = serde_json::to_string(&collection)?;
         self.backend.write(&serialized)?;
         Ok(())
@@ -184,8 +182,7 @@ mod tests {
         let mut backend = MockIJsonDatabaseBackend::new();
         backend.expect_read().times(1).return_once(|| result);
 
-        let mut read_data: Vec<Artist> = vec![];
-        JsonDatabase::new(backend).load(&mut read_data).unwrap();
+        let read_data: Vec<Artist> = JsonDatabase::new(backend).load().unwrap();
 
         assert_eq!(read_data, expected);
     }
@@ -207,9 +204,8 @@ mod tests {
         let mut database = JsonDatabase::new(backend);
 
         let write_data = COLLECTION.to_owned();
-        let mut read_data: Vec<Artist> = vec![];
         database.save(&write_data).unwrap();
-        database.load(&mut read_data).unwrap();
+        let read_data: Vec<Artist> = database.load().unwrap();
 
         assert_eq!(write_data, read_data);
     }

src/database/mod.rs

@@ -2,11 +2,11 @@
 
 use std::fmt;
 
-use serde::{de::DeserializeOwned, Serialize};
-
 #[cfg(test)]
 use mockall::automock;
 
+use crate::Collection;
+
 #[cfg(feature = "database-json")]
 pub mod json;
 
@@ -14,21 +14,21 @@ pub mod json;
 #[cfg_attr(test, automock)]
 pub trait IDatabase {
     /// Load collection from the database.
-    fn load<D: DeserializeOwned + 'static>(&self, collection: &mut D) -> Result<(), LoadError>;
+    fn load(&self) -> Result<Collection, LoadError>;
 
     /// Save collection to the database.
-    fn save<S: Serialize + 'static>(&mut self, collection: &S) -> Result<(), SaveError>;
+    fn save(&mut self, collection: &Collection) -> Result<(), SaveError>;
 }
 
 /// Null database implementation of [`IDatabase`].
 pub struct NullDatabase;
 
 impl IDatabase for NullDatabase {
-    fn load<D: DeserializeOwned + 'static>(&self, _collection: &mut D) -> Result<(), LoadError> {
-        Ok(())
+    fn load(&self) -> Result<Collection, LoadError> {
+        Ok(vec![])
     }
 
-    fn save<S: Serialize + 'static>(&mut self, _collection: &S) -> Result<(), SaveError> {
+    fn save(&mut self, _collection: &Collection) -> Result<(), SaveError> {
         Ok(())
     }
 }
@@ -94,16 +94,13 @@ mod tests {
     #[test]
     fn no_database_load() {
         let database = NullDatabase;
-        let mut collection: Vec<String> = vec![];
-        assert!(database.load(&mut collection).is_ok());
-        assert!(collection.is_empty());
+        assert!(database.load().unwrap().is_empty());
     }
 
     #[test]
     fn no_database_save() {
         let mut database = NullDatabase;
-        let collection: Vec<String> = vec![];
-        assert!(database.save(&collection).is_ok());
+        assert!(database.save(&vec![]).is_ok());
     }
 
     #[test]

src/lib.rs

@@ -928,8 +928,7 @@ impl<LIB: ILibrary, DB> MusicHoard<LIB, DB> {
 
 impl<LIB, DB: IDatabase> MusicHoard<LIB, DB> {
     pub fn load_from_database(&mut self) -> Result<(), Error> {
-        let mut database_collection: Collection = vec![];
-        self.database.load(&mut database_collection)?;
+        let mut database_collection = self.database.load()?;
         Self::sort(&mut database_collection);
 
         let collection = mem::take(&mut self.collection);
@@ -1959,10 +1958,7 @@ mod tests {
         database
             .expect_load()
             .times(1)
-            .return_once(|coll: &mut Collection| {
-                *coll = COLLECTION.to_owned();
-                Ok(())
-            });
+            .return_once(|| Ok(COLLECTION.to_owned()));
 
         let mut music_hoard = MusicHoardBuilder::default()
             .set_library(library)
@@ -2044,7 +2040,7 @@ mod tests {
         database
             .expect_load()
             .times(1)
-            .return_once(|_: &mut Collection| database_result);
+            .return_once(|| database_result);
 
         let mut music_hoard = MusicHoardBuilder::default()
             .set_library(library)

src/main.rs

@@ -15,7 +15,7 @@ use musichoard::{
         },
         ILibrary, NullLibrary,
     },
-    Collection, MusicHoardBuilder, NoDatabase, NoLibrary,
+    MusicHoardBuilder, NoDatabase, NoLibrary,
 };
 
 mod tui;
@@ -85,7 +85,7 @@ fn with_database<LIB: ILibrary>(db_opt: DbOpt, builder: MusicHoardBuilder<LIB, N
             Ok(f) => {
                 drop(f);
                 JsonDatabase::new(JsonDatabaseFileBackend::new(&db_opt.database_file_path))
-                    .save::<Collection>(&vec![])
+                    .save(&vec![])
                     .expect("failed to create empty database");
             }
             Err(e) => match e.kind() {

tests/database/json.rs

@@ -36,8 +36,7 @@ fn load() {
     let backend = JsonDatabaseFileBackend::new(&*DATABASE_TEST_FILE);
     let database = JsonDatabase::new(backend);
 
-    let mut read_data: Vec<Artist> = vec![];
-    database.load(&mut read_data).unwrap();
+    let read_data: Vec<Artist> = database.load().unwrap();
 
     let expected = COLLECTION.to_owned();
     assert_eq!(read_data, expected);
@@ -53,8 +52,7 @@ fn reverse() {
     let write_data = COLLECTION.to_owned();
     database.save(&write_data).unwrap();
 
-    let mut read_data: Vec<Artist> = vec![];
-    database.load(&mut read_data).unwrap();
+    let read_data: Vec<Artist> = database.load().unwrap();
 
     assert_eq!(write_data, read_data);
 }