How can I bind Enum Rust type to Postgres enum in diesel

[YievCkim]

Hi,

I have this schema:

CREATE TYPE profile AS ENUM ('web', 'user-agent-based', 'native');

CREATE TABLE clients (
  id SERIAL PRIMARY KEY,
  client_id VARCHAR NOT NULL UNIQUE,
  client_profile profile NOT NULL
);

pub mod sql_types {
    #[derive(diesel::query_builder::QueryId, Clone, diesel::sql_types::SqlType)]
    #[diesel(postgres_type(name = "profile"))]
    pub struct Profile;
}

diesel::table! {
    use diesel::sql_types::*;
    use super::sql_types::Profile;

    clients (id) {
        id -> Int4,
        client_id -> Varchar,
        client_profile -> Profile,
    }
}

I am trying to find a way to work with this enum type in the model and I don't understand how to write ToSql. I tried this:

#[derive(Debug, Clone, Copy, AsExpression)]
#[diesel(sql_type = sql_types::Profile)]
pub enum Profile {
    Web,
    UserAgentBased,
    Native,
}

impl<DB> ToSql<sql_types::Profile, DB> for Profile
where
    DB: Backend,
{
    fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, DB>) -> serialize::Result {
        match self {
            Profile::Web => "web".to_owned().to_sql(out),
            Profile::UserAgentBased => "user-agent-based".to_owned().to_sql(out),
            Profile::Native => "native".to_owned().to_sql(out),
        }
    }
}

#[derive(Queryable, Selectable)]
#[diesel(table_name = clients)]
#[diesel(check_for_backend(diesel::pg::Pg))]
pub struct Client {
    pub id: i32,
    pub client_id: String,
    pub client_profile: Profile,
}

The build fails with these errors:

error[E0277]: the trait bound `model::Profile: diesel::deserialize::FromSqlRow<schema::sql_types::Profile, diesel::pg::Pg>` is not satisfied
  --> src/model.rs:68:25
   |
68 |     pub client_profile: Profile,
   |                         ^^^^^^^ the trait `diesel::Queryable<schema::sql_types::Profile, diesel::pg::Pg>` is not implemented for `model::Profile`, which is required by `model::Profile: diesel::deserialize::FromSqlRow<schema::sql_types::Profile, diesel::pg::Pg>`

error[E0277]: the trait bound `std::string::String: diesel::serialize::ToSql<_, DB>` is not satisfied
  --> src/model.rs:55:46
   |
55 |             Profile::Web => "web".to_owned().to_sql(out),
   |                                              ^^^^^^ the trait `diesel::serialize::ToSql<_, DB>` is not implemented for `std::string::String`
   |

Is it possible to use string instead integer ? Could you give me an example ?

[weiznich]

There is a complete example here in the repo.
You also might want to look at diesel-derive-enum

[YievCkim]

Thank you @weiznich I am going to try this.

[YievCkim]

It works thank you !