Output formand and unwraps

[fabioluciano]

I have the follow entities configured im my project

And i'm using rocket to create a api to get the results from the database. From a specific scenario i want to get a URL and the related associated tags. I create the following code:

#[get("/url/<id_url>")]
async fn get_url_by_id(id_url: i32) -> Json<(JsonValue, std::option::Option<JsonValue>)> {
    let connection = get_connection().await;
    Json(
        Url::find_by_id(id_url)
            .find_with_related(Tag)
            .into_json()
            .one(&connection)
            .await
            .unwrap()
            .unwrap(),
    )
}

The code works, but i have some issues to address...

1. The result Json looks like this:

[
   {
      "id":364,
      "url":"http://www.arewewebyet.org/"
   },
   {
      "id":5,
      "tag":"rust"
   }
]

How can i return something like...

{
   "id":364,
   "url":"http://www.arewewebyet.org/",
   "tags":{
      "id":5,
      "tag":"rust"
   }
}

2. The two unwraps in the end of the code seems weird, and wrong. There is any other way to do this?

[ikrivosheev]

@fabioluciano I see Many-to-Many relation. Did you mean:

{
   "id":364,
   "url":"http://www.arewewebyet.org/",
   "tags": [
     {
        "id":5,
        "tag":"rust"
     },
     {
       "id": 5,
       "tag": "rust"
     }
   ]
}

[fabioluciano]

Yes, sorry.

[ikrivosheev]

Hmm, I think serde can helps you:

#[derive(Deserialize)]
struct Responsel {
    #[serde(flatten)] 
    url: Url,
    tags: Vec<Tag>,
}

I wrote some proposal: #739 In the future this can help with tasks like this.

[fabioluciano]

I tried to do what you said, but i think that i need to study rust a little more hehehe...

#[macro_use]
extern crate rocket;

use common::database::get_connection;
use rocket::serde::{json::Json, Deserialize};
use sea_orm::EntityTrait;
use sea_orm::JsonValue;

use entity::tag::Entity as Tag;
use entity::url::Entity as Url;

#[derive(Deserialize)]
#[serde(crate = "rocket::serde")]
struct UrlTagResponse {
    url: Url,
    tags: Vec<Tag>,
}

#[get("/url")]
async fn get_all_urls() -> Json<Vec<JsonValue>> {
    let connection = get_connection().await;
    Json(Url::find().into_json().all(&connection).await.unwrap())
}

#[get("/url/<id_url>")]
async fn get_url_by_id(id_url: i32) -> Json<(JsonValue, std::option::Option<JsonValue>)> {
    let connection = get_connection().await;
    Json(
        Url::find_by_id(id_url)
            .find_with_related(Tag)
            .into_json()
            .one(&connection)
            .await
            .unwrap()
            .unwrap(),
    )
}
#[get("/url/<id_url>/tag")]
async fn get_url_tags_by_id(id_url: i32) {
    let connection = get_connection().await;
    let url = Url::find_by_id(id_url)
        .find_with_related(Tag)
        .into_json()
        .one(&connection)
        .await;
}

#[launch]
fn rocket() -> _ {
    rocket::build().mount(
        "/",
        routes![get_all_urls, get_url_by_id, get_url_tags_by_id],
    )
}

My entities are setted like this

use rocket::serde::{Deserialize, Serialize};
use sea_orm::entity::prelude::*;

#[derive(Clone, Debug, PartialEq, DeriveEntityModel, Serialize, Deserialize)]
#[serde(crate = "rocket::serde")]
#[sea_orm(table_name = "urls")]
pub struct Model {
    #[sea_orm(primary_key)]
    pub id: i32,
    #[sea_orm(unique)]
    pub url: String,
}

#[derive(Copy, Clone, Debug, EnumIter)]
pub enum Relation {}

impl Related<super::tag::Entity> for Entity {
    fn to() -> RelationDef {
        super::url_tag::Relation::Tag.def()
    }

    fn via() -> Option<RelationDef> {
        Some(super::url_tag::Relation::Url.def().rev())
    }
}

impl RelationTrait for Relation {
    fn def(&self) -> RelationDef {
        panic!("No RelationDef")
    }
}

impl ActiveModelBehavior for ActiveModel {}

I got some errors, and i read that i need to use the same serde from rocket, so i added

use rocket::serde::{Deserialize, Serialize};

and

#[serde(crate = "rocket::serde")]

as mentioned here

but i still getting some errors

note: required by a bound in `next_element`
    --> /Users/fabioluciano/.cargo/registry/src/github.com-1ecc6299db9ec823/serde-1.0.137/src/de/mod.rs:1725:12
     |
1725 |         T: Deserialize<'de>,
     |            ^^^^^^^^^^^^^^^^ required by this bound in `next_element`

error[E0277]: the trait bound `entity::prelude::Url: Deserialize<'_>` is not satisfied
    --> crates/server/src/main.rs:15:5
     |
15   |     url: Url,
     |     ^^^^^^^^ the trait `Deserialize<'_>` is not implemented for `entity::prelude::Url`
     |
     = help: the following other types implement trait `Deserialize<'de>`:
               &'a RawStr
               &'a UncasedStr
               &'a [u8]
               &'a rocket::form::name::Key
               &'a rocket::form::name::Name
               &'a rocket::serde::json::serde_json::value::RawValue
               &'a std::path::Path
               &'a str
             and 218 others

[ikrivosheev]

Because you need to derive Url and Tag.

[fabioluciano]

It is already derived. Take a look at the entity code above.

[ikrivosheev]

No, rust compiler thinks differently:

 url: Url,
     |     ^^^^^^^^ the trait `Deserialize<'_>` is not implemented for `entity::prelude::Url`

You need add derive to Url and Tag

[billy1624]

Wait... shouldn't this be...?

#[derive(Deserialize)]
#[serde(crate = "rocket::serde")]
struct UrlTagResponse {
    url: entity::url::Model,
    tags: Vec<entity::tag::Model>,
}

What you want to return was the Model, correct?

[fabioluciano]

You are right @billy1624. I was revising the code, and figure out that I'm serializing the model, not the entity.

But, after all, the problem with the serialization is fixed, but another one appears. This code produces a tuple, so I can't use the struct like this.

[fabioluciano]

Finally i figured out a solution! I dont know if is the best one, but worked. Maybe in the future, i'll find a better one heheheh

Firts, define a struct like this

#[derive(Serialize, Debug)]
#[serde(crate = "rocket::serde")]
struct UrlTagResponse {
    #[serde(flatten)]
    url: entity::url::Model,
    tags: Vec<entity::tag::Model>,
}

And a method like this

#[get("/url/<id_url>")]
async fn get_url_by_id(id_url: i32) -> Value {
    let connection = get_connection().await;
    let model = entity::url::Entity::find_by_id(id_url)
        .find_with_related(entity::tag::Entity)
        .all(&connection)
        .await
        .unwrap_or_default()[0]
        .to_owned();

    json!(UrlTagResponse {
        url: model.0,
        tags: model.1,
    })
}

Will produce a output like this:

{
   "id":368,
   "tags":[
      {
         "id":6,
         "tag":"ebpf"
      },
      {
         "id":7,
         "tag":"observability"
      },
      {
         "id":8,
         "tag":"tracing"
      }
   ],
   "url":"https://ebpf.io/"
}

[billy1624]

That's clean! Thanks for the updates