Generic update

[aymanalqadhi]

Hi everyone!
I was trying to implement a generic repository, and I have succeeded so far. However, I get an error when trying to implement a generic update function

My generic update code:

fn update(&self, item: T) -> Result<T>
where
    T: IntoUpdateTarget + AsChangeset<Target = T::Table>,
    Update<T, T>: LoadQuery<DbPooledConnection, T>,
{
    Ok(diesel::update(item.clone())
        .set(item)
        .get_result(&self.get_connection()?)?)
}

An example model:

#[derive(
    AsChangeset,
    Clone,
    Debug,
    Deserialize,
    Identifiable,
    Insertable,
    Queryable,
    Serialize,
)]
pub struct Service {
    #[serde(skip)]
    pub id: KeyType,
    pub title: String,
    pub description: String,
    pub available_begin: Option<chrono::NaiveTime>,
    pub available_end: Option<chrono::NaiveTime>,
}

The error I get when calling the update function:

137 |   self.ctx.services().update(service)?;
    |                       ^^^^^^ the trait `diesel::associations::Identifiable` is not implemented for `Service`

[weiznich]

This error is expected as #[derive(Identifiable)] generates the following impl:

impl<'a> Identifiable for &'a Service {
 // …
}

As the corresponding IntoUpdateTarget impl assumes that the type implements Identifiable this implies that the type must be a reference (or you must provide a manual impl of Identifiable for your type itself.) In concequence this means that the bound T: IntoUpdateTarget + AsChangeset<Target = T::Table> is not fulfilled.

As your code example is extremely incomplete it's hard to exactly tell how to solve this. You can either try to add an manual impl of Identifiable to your Service struct or try to adjust that trait bound so that at least the IntoUpdateTarget part is bound to an reference.

[aymanalqadhi]

Thanks a lot. I solved the issue by providing a manual implementation of Identifiable to Service.