From 1a3fedc78fbd4ad2724f79fdaff354374965a55a Mon Sep 17 00:00:00 2001
From: Rob Ede <robjtede@icloud.com>
Date: Mon, 13 Mar 2023 17:58:08 +0000
Subject: [PATCH] update database examples

---
 examples/Cargo.toml            |  3 +-
 examples/databases/Cargo.toml  |  3 ++
 examples/databases/src/main.rs | 92 +++++++++++++++++++++++-----------
 3 files changed, 68 insertions(+), 30 deletions(-)

diff --git a/examples/Cargo.toml b/examples/Cargo.toml
index 742c070..389cba0 100644
--- a/examples/Cargo.toml
+++ b/examples/Cargo.toml
@@ -2,6 +2,7 @@
 members = [
   "application",
   "async-handlers",
+  "databases",
   "easy-form-handling",
   "either",
   "errors",
@@ -23,5 +24,3 @@ members = [
   "url-dispatch",
   "websockets",
 ]
-# TODO: update databases
-exclude = ["databases"]
diff --git a/examples/databases/Cargo.toml b/examples/databases/Cargo.toml
index 276e6a2..b17a4aa 100644
--- a/examples/databases/Cargo.toml
+++ b/examples/databases/Cargo.toml
@@ -5,3 +5,6 @@ edition = "2018"
 
 [dependencies]
 actix-web = "4"
+diesel = { version = "2", features = ["sqlite", "r2d2"] }
+serde = { version = "1", features = ["derive"] }
+uuid = { version = "1", features = ["v4"] }
diff --git a/examples/databases/src/main.rs b/examples/databases/src/main.rs
index efffd29..55efa1e 100644
--- a/examples/databases/src/main.rs
+++ b/examples/databases/src/main.rs
@@ -1,43 +1,76 @@
+use std::io;
+
+use actix_web::{error, web, App, HttpResponse, HttpServer, Responder};
+use diesel::{prelude::*, r2d2, Insertable, Queryable, SqliteConnection};
+use serde::Serialize;
+
+mod schema {
+    diesel::table! {
+        users {
+            id -> VarChar,
+            name -> VarChar,
+        }
+    }
+}
+
+#[derive(Debug, Serialize, Queryable)]
+struct User {
+    id: String,
+    name: String,
+}
+
 // <handler>
-fn insert_new_user(db: &SqliteConnection, user: CreateUser) -> Result<User, Error> {
-    use self::schema::users::dsl::*;
+#[derive(Debug, Insertable)]
+#[diesel(table_name = self::schema::users)]
+struct NewUser<'a> {
+    id: &'a str,
+    name: &'a str,
+}
+
+fn insert_new_user(
+    conn: &mut SqliteConnection,
+    user_name: String,
+) -> diesel::QueryResult<User> {
+    use crate::schema::users::dsl::*;
 
     // Create insertion model
-    let uuid = format!("{}", uuid::Uuid::new_v4());
-    let new_user = models::NewUser {
-        id: &uuid,
-        name: &user.name,
+    let uid = format!("{}", uuid::Uuid::new_v4());
+    let new_user = NewUser {
+        id: &uid,
+        name: &user_name,
     };
 
     // normal diesel operations
     diesel::insert_into(users)
         .values(&new_user)
-        .execute(&self.0)
+        .execute(conn)
         .expect("Error inserting person");
 
-    let mut items = users
-        .filter(id.eq(&uuid))
-        .load::<models::User>(&self.0)
-        .expect("Error loading person");
+    let user = users
+        .filter(id.eq(&uid))
+        .first::<User>(conn)
+        .expect("Error loading person that was just inserted");
 
-    Ok(items.pop().unwrap())
+    Ok(user)
 }
 // </handler>
 
 // <main>
-type DbPool = r2d2::Pool<ConnectionManager<SqliteConnection>>;
+type DbPool = r2d2::Pool<r2d2::ConnectionManager<SqliteConnection>>;
 
 #[actix_web::main]
 async fn main() -> io::Result<()> {
-    // Create connection pool
+    // connect to SQLite DB
+    let manager = r2d2::ConnectionManager::<SqliteConnection>::new("app.db");
     let pool = r2d2::Pool::builder()
         .build(manager)
-        .expect("Failed to create pool.");
+        .expect("database URL should be valid path to SQLite DB file");
 
-    // Start HTTP server
+    // start HTTP server on port 8080
     HttpServer::new(move || {
-        App::new().app_data(web::Data::new(pool.clone()))
-            .resource("/{name}", web::get().to(index))
+        App::new()
+            .app_data(web::Data::new(pool.clone()))
+            .route("/{name}", web::get().to(index))
     })
     .bind(("127.0.0.1", 8080))?
     .run()
@@ -46,18 +79,21 @@ async fn main() -> io::Result<()> {
 // </main>
 
 // <index>
-async fn index(pool: web::Data<DbPool>, name: web::Path<(String)>) -> impl Responder {
-    let name = name.into_inner();
+async fn index(
+    pool: web::Data<DbPool>,
+    name: web::Path<(String,)>,
+) -> actix_web::Result<impl Responder> {
+    let (name,) = name.into_inner();
 
     let user = web::block(move || {
-      let conn = pool.get().expect("couldn't get db connection from pool");
-      actions::insert_new_user(&conn, &user)
-        .await
-        .map_err(|e| {
-            eprintln!("{}", e);
-            HttpResponse::InternalServerError().finish()
-        }
-    })?;
+        // Obtaining a connection from the pool is also a potentially blocking operation.
+        // So, it should be called within the `web::block` closure, as well.
+        let mut conn = pool.get().expect("couldn't get db connection from pool");
+
+        insert_new_user(&mut conn, name)
+    })
+    .await?
+    .map_err(error::ErrorInternalServerError)?;
 
     Ok(HttpResponse::Ok().json(user))
 }