How to split and loop over strings inside a match in rust - rust

Question

I'm just starting to learn Rust and built a sample api project using Rocket and rusqlite. I want to get all of the items in my database through a get endpoint. My table has an id field and a string which is a list of ids seperated by ,. After getting this back I want to split this string and go back to the database for each entry and then create a struct for it. I'm having trouble figuring this out in a functional way for rust. Does anyone have any advice for how to proceed? I want to manipulate the data myself and avoid orm tools like diseil.
data.rs
use serde::{Deserialize, Serialize};
#[derive(Serialize)]
pub struct Item {
pub id: i32,
pub time_tp_prepare: i32,
pub name: String
}
#[derive(Serialize)]
pub struct Table {
pub id: i32,
pub items: Vec<Item>
}
#[derive(Serialize)]
pub struct StatusMessage {
pub message: String
}
database.rs
use rusqlite::Result;
pub struct ItemData {
pub id: i32,
pub time_tp_prepare: i32,
pub name: String
}
pub struct TableData {
pub id: i32,
pub itemIds: String
}
pub fn setup_db() -> Result<String, String>{
let db_connection = match rusqlite::Connection::open("data.sqlite") {
Ok(connection) => connection,
Err(_) => {
return Err("Cannot connect to database.".into());
}
};
match db_connection
.execute(
"create table if not exists item (
id integer primary key,
name varchar(64) not null,
preperation_time integer not null
);
create table if not exists restaurant_table (
id integer primary key,
items varchar(64) not null",
[]
) {
Ok(success) => Ok("Successfully created database tables.".into()),
Err(_) => return Err("Could not run create table sql".into())
}
}
main.rs
#![feature(proc_macro_hygiene, decl_macro)]
#[macro_use]
extern crate rocket;
use rocket_contrib::json::Json;
use rusqlite::Result;
mod database;
mod data;
#[get("/api/get-all-tables-v1")]
fn get_all_tables() -> Result<Json<data::Table>, String> {
let db_connection = match rusqlite::Connection::open("data.sqlite") {
Ok(connection) => connection,
Err(_) => {
return Err("Cannot connect to database.".into());
}
};
let mut statement = match db_connection.prepare("select id, items from restaurant_table;") {
Ok(statement) => statement,
Err(_) => return Err("Failed to prepare query.".into())
};
let results = statement.query_map([], |row| {
Ok(database::TableData {
id: row.get(0)?,
itemIds: row.get(1)?
})
});
match results {
Ok(rows) => {
///// This is where I'm stuck on what to do next //////
let collection: rusqlite::Result<Vec<data::Item>> = rows.collect();
match collection {
Ok(items) => Ok(Json(data::Table { items })),
Err(_) => Err("Could not collect items.".into())
}
},
Err(_) => Err("Failed to fetch items.".into())
}
}
fn main() {
match database::setup_db() {
Ok(_) => luanch_server(),
Err(error) => eprintln!("Program failed to start because of Error {}.", error)
}
}
fn luanch_server() {
rocket::ignite().mount("/", routes![get_all_tables]).launch();
}

Answer 1

I figured it out and I will post the code here in case anyone finds it in the future. It is not great code and I ended up not using it but it was a good learning experience.
for row in rows.into_iter().flatten() {
let ids = row.itemIds.split(",");
for id in ids {
let mut item_statement = db_connection
.prepare("select * from item where id = :id;")
.expect("Failed to prepare query.");
let mut item_rows = item_statement
.query_named(rusqlite::named_params!{ ":id": id })
.expect("Select item statement failed");
while let Some(item_row) = item_rows
.next()
.expect("Row Failed.") {
let item = data::Item {
id: row.get(0),
time_to_prepare: row.get(1),
name: row.get(2)
};
if !tables.contains(item.id) {
tables.insert(item);
}
}